It's horrifically terrible on Xorg. It's not bad on Wayland.
for example in the image there are 2 monitors above the laptop with the laptop being a 3rd screen, assuming they are all 1080p, x/wayland sees that as 3840 x 2160, then in effect attemts to block out 540 px on either side of the lower monitor, that only works sometimes
Then the shit really hits the fan when you go to play a game, windows is always very good about going full screen only on the primary monitor. X Wayland, I have no idea how it chooses were to go,
also placing things gets really weird if you monitors are out of order, as 0x0 coordinate may not be where you think it is...
There is just 1000 little things that deep in the core of X that were carried over in Wayland that makes multimonitor support poor in Linux, and I dont think it will ever change.
I'm not sure if the issue you're having is with the compatibility layer or the desktop environment support or what, but Wayland shouldn't have that issue and your experience doesn't match mine.
You got those mixed up.
I am both joking and dead serious. Which is why the graphics ecosystem should be indicted: engineers are far too keen to conveniently exclude user stories (or be fundamentally uninterested in them) to document to 1001 corner cases they should be covering with tons of nasty code, instead of finding and optimizing for the One True Way. Nothing changed with Wayland. Xorg is dead, long live Xorg.
I have no issues, and haven't had any issues with Gnome for a long time.
KDE is great, and is highly customisable, but that also means it has a lot of footguns.
And maybe I'm just the luckiest guy, but I can't get Windows 11 to project between my two displays: a 14" 1080P 60Hz eDP panel and the 42" above. I've only spent enough time in Windows to know that the eDP panel doesn't work there, but I for certain don't care to wrangle with any of the different utilities, cleaners, and interfaces when it just works elsewhere.
Every platform has issues. I prefer Linux when I get a choice simply because it aligns with my values.
This is exclusively an issue with Xorg. (as the other commenter also mentioned), the Wayland OOB experience is pretty solid these days, as much hate as Wayland got these are the real problems that it was designed to solve properly.
I would love to hear other complains, 100% linux to 100% windows is quite a strong transition, definitely not one I'd be comfortable making so your situation must have been mired with issues much larger than feeble mixed DPI support; because honestly speaking Windows has significantly larger issues than that.
There are issues like the requirement of a microsoft account, there are issues with snapping windows and global hotkeys and every piece of software needing its own bespoke update mechanism (often interrupting you while doing things).
Theres issues with ransomware, theres deep seated issues with the default filesystem which not only has abysmal performance but also does absurd cache things making it behave extremely strangely with even minor bit flips. I have never experienced inaccessible files except on windows. The permissions system btw requires a damn PhD to understand if you have more than one user on the system.
Or the fact that errors are by default opaque and hidden, the event logger is practically useless both providing no information relevant to the issue and simultaneously far too much information so you drown in irrelevance.
As a power user, windows is about as hostile as it possibly could be.
As a normal user the experience is really unclean, the 17 pop-ups I get when installing and the forced online account are enough, but honestly the weight of the OS is so much: you literally cant even run the thing on a standard spinning drive anymore.
Today, 100% on Linux (Arch btw + KDE). (It's been years since I booted into my Windows drive. I don't even know if I remember the password.)
To me, using monitors of the same size (not that I've ever not done that) is a tiny price to pay for an OS meant for engineering and that doesn't fume with spyware and condescension for me. (That said, I wouldn't've survived long without Valve supporting Linux. :p)
Today I am 100% windows desktop.
Linux still suffers from the same problems it did when I left, terrible multi monitor support. Right now I am running 4 Monitors, an UltraWide, 1080p Landscape, 4K Landscape, and a 1920x1200 portrait mode. This configuration of different sizes of montiors, in different orientations has always been, and continues to be a nightmare on linux.
Windows has the absolute best multi-monitor support, and even after going with an UltraWide I still find I want many montiors