Comment by WhyNotHugo

Multiple displays with different scales has worked fine since at least 2017 (which is when I stated using sway, and precisely for this reason).

OTOH, I know that recent versions of GNOME struggle with this. Just last year I saw plenty of situations where moving windows across displays triggered all kind of quirks. This is a GNOME-specific issue, and like most of its issues, doesn't affect all other compositors.