I mostly do indie games, and I do fine on a Mac (I have several different OS at home, majority Linux). But, my 2017 iMac with aftermarket 32gb RAM can run BG3 on the lowest settings.
FPS? No idea. I don't play games for the visuals at all, and if you gifted me a high end gaming PC I still wouldn't. It's not a question of superiority or inferiority, it's just down to taste.