Do not use skins. They can mess up the finish of the plastic. But a good quality screen protector will not harm the screen itself. In fact it will keep it nice.Thats what i read that screen protectors and skins on the switch is a bad idea,maybe the glass screen protectors work better dunno
NOTE: people have reported that the Hori Premium screen protector is melting. I think it's because the premium one is thicker, and not letting heat disperse as well as thinner ones. Ironically, thinner protectors like Horis own cheaper regular ones, and the even less costly Illumishields are not having a problem.