I’m also using Plasma 5 on my Surface Laptop Studio! Wayland brought a lot of touch advances, but unfortunately the onscreen keyboard still does not work with every application.
Personally, I think KDE Plasma is great for convertibles/touchscreen laptops, but still has a ways to go before I’m comfortable using it with touch on the Surface. Windows 11 is still the best “touch-optimized desktop environment” I’ve used, unfortunately, but I’m expecting good things as more apps are ported to Wayland!
For my SLS running EndeavourOS it works flawlessly…but not out of the box! I had to search and install the proper codecs to stop YouTube in Firefox from using all my CPU