In the systemsettings we have now the scaling factor in Plasma-Wayland. On my 4k norebook screen it is automatically set to 2x. If I changee to 1x and reboot (what I have to do as the wallpaper is shown only on 1 quarter of the screen after changing the setup), then it is defaulting again to 2x. First this value should be remembered. And second I think it should be adjustable to other values like for example 1.7x. On my 4k notebook screen with 2x scaling fonts look to big. On X11 I don't see the scaling factor at all. X11 and Wayland seem to handle scaling factors as well different. Using one configuration for both is impossible at the moment at least from what I have seen at the moment.
Thanks. Will fix soon. Yes they use separate configs. It's pretty much unavoidable as the behaviour is different. As for fonts looking too big, on Wayland you should turn off "force fonts DPI". That's also moved into a separate config for 5.11.0 to make it easier to go back and forth. *** This bug has been marked as a duplicate of bug 384733 ***