Maybe I do need to check out xfce, then. I use kfe, and I'm often frustrated by the ui freezing, and the mouse cursor slows down a lot. Sometimes the delay between clicking and something happening is seconds. I'm baffled at how modern OSs can be so bad at ui (because Windows and Mac do it too.)
This kind of stuff was happening to me maybe 2 years ago on Plasma 5 with X11 (I can't believe Plasma 6 is two years old now!). After I switched to Wayland during the Plasma 6 upgrade, the DE has been buttery smooth and most of the major bugs were gone.