Scrolling on Wayland is choppy unless, e.g., one sets in the GUI "mouse wheel scrolls by" to 1 line, rather than the default 3, for example. This is true for both gtk and qt(5) apps. I'm using an Elan touchpad.
My elantech touchpad works fine on neon dev, Wayland session. I use two fingers to scroll.
Is Neeon Dev using Plasma 5.10? And were any input changes made in 5.10? Is your scrolling experience *exactly the same* under Wayland and X11?
Neon dev runs plasma 5.10.90 here. Scrolling is a bit faster under Wayland. Scrolling sometimes becomes choppy on Discover app under Wayland.
I'm now on 5.10.0 and scrolling is actually worse than it was on 5.9.5. It's so bad, I can't use wayland as my default session. I'm not sure what's going on, but touchpad scrolling behavior is completely different on wayland than it is on X.
The setting is completely irrelevant for GTK applications. Thus I have to doubt that it has any influence. This cannot be a bug in KWin as we only take the events from libinput and forward them to the applications. Thus it's either a problem in libinput or in the applications. Marking as invalid for kwin.
I guess it's an issue with libinput, since it's used in wayland but not X11 in Neon (as far as I'm aware).