While Wayland support in the proprietary NVIDIA driver was quite rocky a few years ago, it has matured tremendously. Graphics cards still supported by the manufacturer work just fine nowadays
And here is me with the latest Nvidia card/drivers/Plasma unable to sign in into Wayland 
Wayland + Nvidia, black screen with cursor
Accessibility is a very broad topic, so it’s hard to make any definite statements, but we’re generally on par with the X11 session. All the basics already work as expected, including screen readers, sticky & bounce keys, zooming in, and so on.
However, accessibility features provided by third-party applications may be worse in some aspects
The problem is that there is no first-party accessibility on-screen keyboard, and most third-party ones are broken (especially non-basic).
For Onboard there is a fork and people say it works with the GDK_BACKEND=x11 flag, though as I understand it breaks some Wayland ideas, not sure if can cause issues. Plasma 6 and Wayland no on-screen keyboard working - #47 by INVICTRA
Also tools that perform any UI manipulation are broken, such as Talon (voice control) wayland-accessibility-notes/talon-requirements.md at main · splondike/wayland-accessibility-notes · GitHub
Maybe a partial workaround could be via ydotool 