Here's what I'll say for Amber regardless of her being inexperienced and weaker (via feats) doesn't really play a factor in what I am going to say.
1. She's able to block/negate/deflect (whichever you prefer) Emerald and Mercury's bullets with her hands. Later she just does it with her chest.
I don't think either is more impressive but take what you will.
2. Even when Mercury and Emerald jump her (partially because she's surprised by Mercury's legs) she's totally fine and tanks it.
3. Although she starts using magic to attack Emerald and Mercury are unperturbed and continue to dodge lightning and take her ice attacks just fine.
4.
Then Cinder dodges a fireball and shoots glass at her and knocks her down. Cinder pursues and gets smacked away,
despite not having eyes active.
5. Emerald and Mercury try again to take her and she's blocking, parrying, and countering everything. Cinder only gets the better of her with her semblance/dust arrow.
6. She can no longer maintain an aura shield but is still fighting. She instantly blows them away with wind (from the hand, not staff). Mercury gets tagged with lightning and Emerald gets hit with a fireball.
Obviously, Cinder impales her afterward.
Summary-
Amber was superior to Emerald, Mercury, and Cinder with or without Maiden powers. But they were still to each other otherwise they wouldn't be taking her attacks or pushing her back in certain instances. Cinder was the only one who could do significant damage to Amber (only with semblance/dust arrow). There isn't any qualitative difference between maiden powers or not. Unless you want to use the blocking but even if you did that doesn't contradict my premise.
Remember that I don't mind that they can amp themselves physically (which is what the contention is, not anything else but physicality). But I don't think you can say it's inherent to the activation of powers. In fact, I think heavily in the opposite favor.
As you pointed out, Cinder does seemingly use her magic to set her fist on fire (1:07) as well as to shoot a small fireball (1:36) and then upon activating her maiden powers at 2:08 Neo immediately gets blown back and notices the gap in their power as just seconds before they were fighting on even grounds when cinder's powers were not active. Note that the same thing happens when Cinder confronts Adam about joining her after she gets the Maiden powers.
Next up is Cinder vs Winter and Penny:
Okay, this one is easy. We could argue about Cinder still having a slight advantage against Neo and her not trying to really hurt her, etc. But that's tired and unnecessary.
As you said Cinder uses her fire twice, both on her fist and firing a fireball. Now the problem with using her pushing Neo back is.....they didn't fight. So you don't have anything to compare to. As for Neo conceding, don't forget the context. Cinder brings up Ruby and tries to convince her which clearly works. It doesn't have to be an intimidation thing
AND even if it was it doesn't necessarily mean she was stronger. It's not like Neo (or anyone else in the series) has a way of determining how strong Cinder is. So, she could simply be intimated or confused by her sudden change in power, heck she starts flying and control the air. Neo saw so wild shit and got out.
The same thing happened on the train against Raven in V2.
Summary-
Neo and Cinder were at least relative in their fight and Cinder pulls out strange powers and abilities that Neo's never seen before. All while Cinder tries to persuade her into helping each other attain her goals. Neo concedes the fight and tries diplomacy instead. Nothing that happens that's inherently indicating Cinder scared Neo because she got more powerful. There are equally, if not more likely interpretations that I have presented. Let's also not forget Cinder at one point, with one leg, parried an attack, kicked her in the face, and pinned her onto the table. Then almost crushed her with her fire fist. And proceeds to compliment her on her strength. It's very possible Cinder could've manhandled Neo with maiden powers.
To quickly cover the Adam thing, if you watch it again you'll notice not only does she never activate her eye flame. She only threatens him and starts a fire BUT her clothes were lite at the time (indicating dust) just like they talked about in V2. And even if she didn't have the dust clothes she can make fires without the eye active.
I actually use that scene in conjunction to prove that Maidens attain an amp upon receiving the powers initially.
Right off the bat Cinder fights on equal footing with Penny and Winter and then the second the activates her maiden powers she casually overpowers both of them simultaneously, especially at 5:20 when she immediately starts dominating Winter in cqc with hr maiden powers. Cinder also uses partial maiden powers to fly but then activates them fully to do anything else at the same time as flying with her being again fought on par with by winter and penny while she is just flying but then going so far as to basically oneshot winter with her full maiden powers.
Now Penny vs the Ace Ops:
For this one imma give a play by play and explain afterward.
- Cinder literally starts the fight bodying Penny by blocking her punch and throwing her into a wall. Winter uses her semblance and tries to tag Cinder but can't connect.
- Cinder activates the maiden powers and her semblance to create her blades. Then immediately deactivates them and starts overwhelming Winter. She quickly dispatches her with a kick and she's down for a period of time.
- Penny comes back and tries to overwhelm Cinder with her amount of blades to no avail. Winter joins and Cinder is parrying and blocking from both while smacking them around.
- Cinder uses her maiden powers to create an explosion under her feet to increase her speed, blitzing Winter and Penny who were already significantly slower than her.
- They begin falling from the window, Cinder deactivates her eyes and start choking out Winter and Penny simultaneously. Winter stabs her and Cinder releases her and Winter falls. Penny gets thrown away by Cinder and she creates her exploding blade (dope as shit btw). Penny barely catches it and it explodes blowing her away.
- Cinder while distracted by Penny and monologuing gets hit by Winter's Manticore summon fireball (ice ball? it's not on fire but Manticore shoots fireballs). Cinder in anger retaliates by activating her eye and firing a fireball. Winter rolls out of the way. Penny and Winter charge Cinder. Cinder parries Winter, Penny attacks Cinder and gets parried. Cinder fires another fireball (eye active). Winter again tags her from behind.
- Cinder quickly recovers and charges Winter. She evades her summon and one-shots it with her blade (no eye). Winter begins falling and Cinder destroys her aura shield with another fireball (eye active).
Before we continue to the second half, Cinder was also flying the entire with flames and no eye. Just for the record.
- Cinder tries absorbing Fria with Grimm arm (though she wasn't really trying to attack her). Cinder frees her arm and makes a blade then activates her eye and gets blown back by Fria.
- Fria's cold wave hits Cinder's Grimm arm and Cinder retreats because screw the cold.
- Winter tries to approach the wave of ice and nearly gets her fingers burned off.
- Cinder blasts through Fria's ice like Bakugo. She lungs her Grimm arm at Penny and Fria. Winter then cuts her arm off while she's not looking.
- Cinder screams in pain and regrows her arm. She actives her eye and begins frantically throwing her swords at Winter which quickly overwhelms her.
I don't think anything else needs to be covered. There isn't much to summarize either. Cinder was already bodying Winter and Penny beforehand, she continued to body them afterward. There also isn't anything that prevented Cinder from lounging at Penny without the eye flame seeing as she flies like that constantly. So it's not a particularly fair comparison, one instance is with flight the other is without. Even disregarding that, it doesn't demonstrate her body getting any more powerful. Lastly, I'd just reiterating what I said either. She already bodied Winter either without any eye and this time Winter's even more tired and drain as well as Penny not aiding her. So I don't see why she couldn't do the same thing with eye active.
Penny opens the fight with full maiden powers, her wind summoned with this casually blowing the ace ops away to the point that harriet's semblance can barely overcome it and elm needs her semblance to not be blown off the platform. Her eyes then stop glowing causing the wind to die down a bit but still exist and Harriet can move freely with her semblance. Then at 1:48 Elm grabs her and the wind dies down completely only for Penny to activate her powers fully and blow the entire team away again.
And now for Penny vs Cinder:
This one doesn't need much. There isn't any evidence of the wind dying down because of her eyes. Or as a result of them. Before Harriet ran over Penny turned around and faced Vine. So it could be her shifting focus that deactivated the wind blowing towards Elm, Harriet, and Marrow. Or she simply can't maintain that wind while fighting them. As for Elm, she gets grabbed and can't breakout. So she builds up her energy to blow Elm and Harriet away. That's totally fine, not really a physicality thing. (Especially since she's a robot so unlike the other maidens she may have not gotten any physical amp) Penny generating more powerful attacks with magic is fine with me. Again all I am concerned with is the notion is that they constantly do it when the eye is active. As well as it amping their physicality (statements in conjunction not separate btw).
Starting from 1:20, Cinder is using hr maiden powers while Penny is not and each hit Cinder lands on her causes her to audibly cry out, whereas later on Penny using her maiden powers is able to fight on par enough with Cinder to throw her away and then laser blast her to incapacitation.
The conclusion? Maidens are able to use minor magic without fully activating their Maiden powers but they dont get a strength amp unless their full powers are active.
This one is just a reach at best. Penny literally just isn't fighting her in the beginning. Obviously, they can harm each other, so her displaying that is fine. Penny fighting her when she simply wasn't isn't really showing me any point of comparison. Especially when she wasn't tanking attacks later on or something. She also specifically mapped her lasers against Cinder so that she could knock her out. Which all falls within the standard, totally fine. Cinder mainly using semblance during the fight anyway and not much magic. (Yes she can combine them) But it then becomes a bit ambiguous to say if ones more powerful or not.
