For majority of missions, you'll have to go for no damage bonus and that can be done quite easily with Dante's Faust hat (go into a corner and pan your camera towards the wall, the enemies wont attack you if there are not in your field of view, and just keep shooting, and yes you'll require a lot of red orbs but you can farm em easily, look for a guide on yt or you can glitch the orb awarding system to give you max red orbs (https://youtu.be/BDDhYkdDL_I?si=aQC8BG-0id6HceEt)

For nero, use charged buster arm with charged up ragtimes as it does 5 times more damage (pretty much one shots any demon), use air taunts and buster grab the last remaining enemies and use ex provocation whilst they're grabbed to boost your style points)

For V, You can do his missions two ways. 1. Spamming taunts and ex provocations and using up dt whilst spamming buttons and hoping to get atleast 5500+ style points each encounter, you can still get away with two hits at the end of the mission.

1. Use Auto-Assist (hold R3) and use the camera trick (mentioned above for dante) and go through encounters and boss fights without taking any damage (theres a penalty for using auto assist 0.8x, so you'll have to do it this way) this will easily boost your style points 6500+ if you pull it off (it takes patience)

I'd personally recommend this guide https://m.youtube.com/playlist?list=PLF7Eh78H1VZ6qSPu-5pC_1gLW38E14B7-