Hi @daab
Seems we are in the same boat. Please check my first post to know what I’m talking about.
Try do what I did (previous posts in this thread). Disable…Disable…Disable… you can enjoy KDE again!
I’ve been on KDE almost all the time.
I can tell now, that KDE though sluggish by default, I just disable all the bells and whistles of windows composting… (as in previous post above), I even disabled everything.
Now it’s incredibly fast… a bit slower than light speed 
And as I been away from Linux for some time, I’ve been installing and trying different distros, the longest could stand maximum 48 hrs!
Now, with Endeavour, KDE Plasma (with all nasty stuff disabled) AND above all the wonderful community here I’m now on my 3rd day and enjoying every moment.
I don’t see any reason to even think if there is another better distro, and just for argument sake only, if there is, I am OK here with this wonderful community.
I hope you enjoy. 
EDIT: The only thing I’m missing is the transparency while dragging a window. I couldn’t figure out yet which option to get it back!