Man, folks talk about all sorts of things that X11 doesn't do. (And you have some manual steps that you do every boot (but (as you say) could easily automate.)
Me? I just have this one file:
cat /etc/X11/xorg.conf.d/20-tearfree.conf
Section "Device"
Identifier "AMD"
Driver "amdgpu"
Option "TearFree" "on"
Option "VariableRefresh" "on"
EndSection
and I get all these things that people say X11 doesn't do:* zero tearing... whether in KDE or WindowMaker
* zero problems with my mixed-DPI displays (one 32" 2160p display, and one 24" 16:10 1200p display)
* zero problems with my mixed-refresh-rate displays (one at 60Hz and one at 59.95) (This one I've tested with my eyes and also with MPV. MPV is 100% aware of the display's refresh rate, and will dynamically get updates to that information as its window moves between the two displays.)
I DO NOT get VRR, because (last I checked) kwin on xorg doesn't support that.
I wonder how many folks who think that this stuff doesn't work are on Nvidia hardware. (Which (by the sound of it) doesn't work all THAT much better on Wayland.) I also wonder how many are on AMD/ATI hardware and don't know about the 'TearFree' option.