Try using mixed DPI displays. My main display is 27 inch 4K display, and on the sides I have old 19 inch 1280x1024 displays, used for IRC, music player, process monitor, email etc. Stuff I glance at from time to time.
_NOTHING_ supports this setup properly. Even Windows has bugs galore as soon as you mix high and low DPI displays. I don't believe anyone ever tests this scenario. I've learned to tolerate and work around the Windows bugs, but I've never gotten it to work at all in any Linux desktop environment I've tried.
I use a 1440p display at 100% and a 4k display at 175% on Windows and it works fine. The only bug that I see is that if a window is spanned across two monitors, it picks the scaling based on which monitor contains more of the window. I'm not even sure that's a bug, it's just how it has to be done. (My first mixed DPI setup was actually on ChromeOS. That got around the issue by not letting a window span monitors. Actually a somewhat elegant workaround, since it didn't let you do that before HiDPI support ;)
Windows and the applications I use even handle the different refresh rates of my monitors pretty well. I have a 165Hz main monitor and a normal 60Hz monitor. Apps are aware of the framerate differences when I move them around.
It wasn't always good, but as time goes forward applications and Windows itself handles HiDPI better and better.
(FWIW, I haven't had any problems on Ubuntu... except that letting the monitors go into power saving mode resets the display scaling override. That was with 18.10, though. I use an Ubuntu VM under Hyper-V now... begrudgingly.)
Having said that, I am not a GUI power user by any means. On Linux, all I ever use are a browser, terminal, and Emacs. On Windows, I use CAD software and games (and a browser, terminal, and Emacs). It all works well enough for me.
I am using a 1200p, a 1800p and a 2160p monitor side-by-side on MacOS and it works fine. The 2160p monitor is rotated to portrait mode for reading/writing text documents. I can hotplug a monitor and it will automatically switch to the right layout, remembering the correct location for all open windows.
I am using a 1080p and a 2160p on ArchLinux/Wayland/Gnome3. It's not perfect, but it's not unusable either (compared to X11, which was completely broken).
_NOTHING_ supports this setup properly. Even Windows has bugs galore as soon as you mix high and low DPI displays. I don't believe anyone ever tests this scenario. I've learned to tolerate and work around the Windows bugs, but I've never gotten it to work at all in any Linux desktop environment I've tried.