I have a 2019 MacBook Pro 16". It had Catalina on it when I first got it, but I recently upgraded to Big Sur and was on 11.6. I was having an issue and opted to reinstall Big Sur from scratch. I did that yesterday and made sure that 11.6 was installed with all available updates applied. Everything seemed fine yesterday, but I've noticed a lot of lag today. It seems to be largely dependent on the application. My guess is some of the applications are making use of Metal and those are fine, but others are using a different framework and the performance is very poor. That's just an educated guess...I don't have anything scientific to back it up. But the reality is I rebuilt and am seeing very poor video performance with a fresh instal of Big Sur 11.6. I was not having this issue prior to rebuilding the laptop. This is very disappointing! At least I'm not alone in seeing this sort of behavior.

@pajp_fsc what version of VMware Fusion are you running?