This week #Plasma has received quite a lot of fixes,
like you can now remove the titlebar and frame from a window directly from the Task Manager, the digital clock gets a nicer-looking font picker dialog, and we have simplified the info shown on Display Configuration, among many other improvements and changes.
https://blogs.kde.org/2025/03/08/this-week-in-plasma-a-very-fixy-week/
Yes. If the cursor is sluggish, there is something wrong. Get yourself to https://discuss.kde.org and ask there.
Yeah, barring any uncommon glitches, KDE has been the smoothest experience I’ve ever had. Especially since they’ve ironed out KDE 6’s quirks with Wayland.