Screws breaking through drywall paper
It depends how far in. Ideally you want it less than 1/8" in. Within 1/2" drywall, that's a decent amount. If you get more than 1/4" in you run the risk of cracking the gypsum underneath and not providing the adhesion.
I don't know about a percentage. I would drive another screw nearby if you over-drive one. Leave both in.