Works with Wayland btw, though still experimental

Not really. The reason is that Steam (and an unfortunate number of other programs) run through Xwayland when your compositor is using Wayland. If you then use fractional scaling, Xwayland will render at the fractional of your resolution and will be scaled linearly to your display. This results in general bluriness for X11 applications.

Kwin, to my knowledge, is the only Wayland compositor that allows decoupling Wayland scaling from Xorg (and does so by default). While this results in different scaling behaviour for X11 apps, it does mean they are never blurry.