Hmmm alright. I suppose me being summoned to this match is fitting given I went with Edelgard’s path the first time I played 3H
Power null won’t work since that’s magic based and I admittedly think the Double Riders have better acrobatics. Edelgard isn’t bad herself, but Ichigo and Nigo are more favourable in agility based on their many showings. There's pretty much nobody in 3H who comes close to their acrobatics (even during this era, Riders could leap to insane heights just in single bounds)
Accelerated Development should be helpful for Edelgard against the 1.3 AP advantage that the Double Riders have. That being said, Rider Power can increase the strength of Takeshi and Ichimonji as well. That's not even counting their own accelerated development
Edelgard's attacks that are fire-based and electricity-based really aren't going to be useful. In fact, both Riders could absorb the fire-based attacks
Now in regards to skill, that is also important to bring up. The Double Riders undoubtedly have a lot more experience than Edelgard does, but experience and skill can't always be compared the same way in each match so I'm gonna go in-depth on the Double Riders. Ichigo and Nigo were capable of defeating
six opponents with the same powers and stats as themselves with strategy alone. This isn't even them at their most experienced. These two spent decades taking on evil organizations that not only had members who fought in wars themselves, but were further enhanced with superhuman strength + abilities along unique threats created by their groups. Ichigo and Nigo fought these kinds of opponents with little to no help. What I'm essentially getting at is that strategists such as Edelgard are not uncommon for them to encounter and they've even taken on those kinds of fighters individually
Edelgard isn't helpless though. In terms of her arsenal, she's got a versatility edge. Stuff like Nosferatu will be effective. I don't think that stat buffs and debuffs are really gonna play a role in either side's victory though since that'll just go back and forth. Nothing is going to stop the LS advantage. This would especially be troublesome if the Double Riders paralyzed her and then got up close. The Supernatural Willpower of Ichigo and Nigo would also help each other in persisting through Edelgard's more potent abilities here
I'm voting Ichigo and Nigo due to their abilities, resistances, skill, experience, and teamwork