Interesting. Apart from the per-display scaling (which is basically a Xorg limitation as you said) I had the opposite experience on my XPS 13. At the end I did

Interesting. Apart from the per-display scaling (which is basically a Xorg limitation as you said) I had the opposite experience on my XPS 13. At the end I did not want a 4K display but Dell did not offer me the option. So I just used 1080p scaled most of the time. Battery life was stupid on Windows (~3-4 hours max, while Linux did 7-8 with moderate load). Somehow on Windows the fan would always be running even without any significant activity in Resource Monitor. I remember playing 4K videos on Linux (Firefox though, and I only tested YouTube) without any trouble (with monitor disconnected though, due to what you described earlier). Touchpad would work sweet on Linux but needed some tweaking on Windows (otherwise it'd 2-finger scroll too fast sometimes).