Interesting! Are you saying Nvidia performance is now better on the latest Catalina version than on any Mojave version? And how does it compare to High Sierra.After the latest update (10.15.4) everything is much better. No more artifacts and performance is fine. Just small lags when switching desktops. Everything else is fine.
Personally I'm still on High Sierra which works quite ok compared to Sierra but with daily graphics glitches where the system freezes for a brief moment.