> And Wayland supports HiDPI with fractured scaling very well

Very well only for the apps that cooperate well, e.g. GTK-based apps.

Non-native apps (eg IntelliJ Idea) on my Ubuntu desktop were blurry when I used any kind of scaling - not just fractional scaling but any scaling != 100%. Reducing the display resolution by 2x resulted in much crispier rendering than full resolution with 2x scaling for those apps.