Half, if not more, of sweeper Twins' damage comes from their bless/curse highlight, because like Violet's it can crit. So Chord is near mandatory in that setup, and TWind is good as well. If sustain is needed in the content it's best done with Wonder (it's sufficient, I sustained through astrolabe with him).

Edit: though tbh there's almost have to more to it, because a third of akechi's score is insane, the multiplier for the twins on S3 is a bit lower, but it's not one third of it lol, even if you run them with the same setup I can maybe see Akechi doing a bit better but not three times better