I have tried Plasma. Imo, it's not even close. X11 style touch works OK in Plasma, but the multi touch gestures for navigation isn't anywhere near as good as Gnome with Wayland. In Gnome, I'm just missing a few quality of life gestures, like being able to swipe from an edge to un-hide the auto-hide dock.
I also tried Plasma Mobile (which was amazing for tablet like navigation), but the hi-DPI scaling was all broken.
I also recently got a Surface Pro 6. I got it used for $200, but it was in great condition, low battery cycles, and came with one of the keyboard covers. As you said, everything works. Gnome in Wayland is pretty good for touchscreen. I also got a third party pen for it that works great in Krita and xournal++.
I wish using it as a tablet was a bit better supported in Gnome or other DEs, and the battery life is only ... OK. Still, as a thin and light linux tablet I can carry in my bag to work on light tasks or look up content it's fantastic. The keyboard cover also makes it great for typing, programming, or opening remote shells on the go.
I'm typing this on my desktop that is running Plasma wayland right now. The touch gestures don't give as much of a tablet experience. It's not that plasma doesn't work. If I want to use it as a "pure tablet" without normal computer interactions with the keyboard at all, then it's not a great fit. Gnome is miles ahead for that use case.