Luckily I asked you to provide a full inxi:
- Upgrade your RAM, because swapping uses a lot of CPU (and CPU in
waitstate)
OR - open less applications and run them at a lower resolution.
You’ve done already the right thing to go back to XFCE as KDE is indeed overkill for your hardware as XFCE is much lighter.
We can do a lot, but we can’t do magic…
