I'm using X11 here for various reasons, without any stuttering or anything. I'm not running KDE, but i3 with a nice helping of compositing, most notably blurred windows. And this isn't even some kind of absurd machine I'm talking about, but a 3 yo "ultrabook" with integrated graphics. WTH does KDE do to stutter?
I have issues on both x11 and Wayland, but the least amount of issues on Wayland.
I think it is mostly because of individual applications, not particularly KDE/Plasma. Some software works better on Wayland, some on x11, some on both.
Sure, let's go with that!