> I had to try three window managers until I was able to use fractional scaling in such a way that my main 4K 32" screen shows 150% and my secondary screen shows a sharp image because Gnome cannot do fractional scaling only on one screen and for some reason 100% resulted in a blurry image.

Does your Gnome install use Xorg? If yes, than it supports this. Xrandr settings are per screen. That is independent from the Window manager.