Debian (stable) user here. I'm also scratching my head trying to understand what bugs you find on KDE. Or what kind of multi-monitor or window behavior you have a problem with when compared to Windows. (Isn't the default window behavior basically equal to Windows? I have never notice a difference in anything that I didn't change myself.)
I too think you were unlucky on your combination of hardware-distro-setup in some unusual way.
HiDPI is not perfect neither in KDE (arguably, better situation)not in Gnome, compared to Win 11. When your enable scaling, window's context menu (left click on menu) is not scaled in debian 12 and Ubuntu, irrespective of environment variables (PLASMA_USE_QT_SCALING=1 and such). In Wayland (which solves many scaling problems) KDE renders fonts blurrier than in X11. For many it is not a big deal, but not is not acceptible for me. Gnome apps are not properly caled unless the scale is bigger than 175%, and then they are too big (overscaled).
I too think you were unlucky on your combination of hardware-distro-setup in some unusual way.