>>372102503
It'll always work as long as you don't go "CATS tool goes brrrr" without knowing what the heck you're doing.
I meant more as in, what's your end goal for getting it into all one mesh? For example, unless you're under 32k tris, VRC will rate a single mesh avatar only as good as one with 70k tris and two skinned meshes. So there's no point in combining everything into a single mesh unless you have less than 32k tris on the avatar so you can shoot for the excellent rating.
And in my experience, going for the excellent rating is a waste of time, since you're losing a lot of detail without gaining anything.
Only reason to optimize that much would be to use it as a fallback, and fallbacks require you to be good/excellent for Quest which means 10k tris, at which point you'll look absolute dogshit.