Without knowing any specifics of your hardware, please note that there is currently at least one open issue that could have a significant impact on desktop effects (stutters etc.) if you are using a HDD for /home.
I guess it will be fixed with one of the next Kwin updates:
In my tests/usage of Plasma 6 on Wayland, everything worked out great so that I felt it was a big improvement to Plasma 5, even if I prefer to use Gnome for my daily needs.