Retainers and mewing

I currently wear Invisalign style retainers and I’ve heard that they stop your jaw from growing because they lock the teeth in place, and since the jaw and teeth are attached I will not get any jaw improvement from mewing.

The big dilemma is having my teeth shift if I don’t wear retainers. My teeth were decently messed up before braces so a relapse wouldn’t be good. My question is if I use correct body posture, mew correctly, and chew correctly will my teeth maintain good position instead of relapsing?

Any input helps, thanks