Are you talking about the Destroyer Glitch? If yes: Defeat Drek > Watch a bit of the end battle cutscene(do not instaskip it) > Skip the cutscene and load a file without hitting the button > Done

There's a new thing with visibomb on poki, yes. I would just quickly select it on the weapons menu during the second ship ride. I think, if you want to be optimal, that's the only place you're gonna use it in NG+, anyway.

The one you're most confortable with. That matters for UYA cause you have to personalize it during the run. In RaC1 however, you already have that done when you start, so it really does not matter