I’m on mobile so formatting might not look the best, but here it goes!
X11 scaling - does this link help? wiki.archlinux.org/title/HiDPISpecifically under either xorg or KDE plasma I think you might be able to find some settings that help
For Wayland - would wdisplays help you out? I’ve had good results using that along with kanshi.
As for system freezing, I’m just taking a shot in the dark but this might be a KDE thing based on a quick search. Wayland is new and sexy, but apparently all the bugs aren’t worked out for KDE. This answer isn’t great, and is very hand-wavey, but without more details outside of you’re on KDE I can’t really help much. Unfortunately for you, I switched over to Sway which apparently has better Wayland support out of the box.