While they are seperate entities, they are extremly similar. If they arent, explain why Arc turns into Neco-Arc in Kagetsu Tohya?
As a gag, those scenes are comedic very obviously, even the wiki which I'm sure is where you're getting this info from, says as much
Explain some characters refer to the Neco-Arc of Melty Blood as if she were Arcueid herself?
Because she looks like Arcueid, again, thats the entire joke.
Explain why she posses a variation of Arceuids technique?
Because that's literally the entire joke/gimmick, she has "variations" similar in name and nothing else at the absolute best, or are completely nonsensical at worst.
Like idk, I'd rather trust Aoko on whether or not Neco Arc is the work of a fellow wizard who she knows the abilities of, than say "actually she's wrong and Neco Arc is actually just Arc".
Hell, even saying "they're similar" doesn't give any grounds to just give her Arc's stuff, that's only really an argument if you're arguing they're the same entity, which they aren't.
Her just having luminous body confirms that she shares many similarities to the True Ancestors
No it does not, because there's nothing suggesting her luminous body is similar, it's just the name from what I remember
Remake Neco is a slightly different entity, though.
No, she explicitly says (and all stuff referencing her says this too) that she is merely the original one upgraded slightly, and that now she's gone from a 0:10 battle ratio to a 5:5 against the same characters, with it being noted that that means she hasn't actually changed at all
Also gag feats have been accepted before, just look at arales entire profile.
Yes, gag feats for a gag character from a gag series is very different from a gag character from an otherwise serious series which would scale to others and be an outlier if taken seriously, this is a massive false equivalency
Well it was discussed, and it was agreed that it doesn't physically scale to anyone. Neco Arc is shown flying away from the blast, so its heavily implied she wasn't caught in it anyways. The bomb getting the rating should be fine though.
The issue is there's other ways to scale it to her besides her being hit by the blast or not which were brought up last time (Neco Akiha and her explicitly having all the same abilities, and them saying it'd be an infinite stalemate, implying that attack wouldn't beat either of them, a similar thing happening with Neco Ciel, etc)