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X11 has never been 'stable', in my experience. It's janky as all fuck. Constant stuttering and tearing, and looks slightly different on every piece of hardware, even from the same manufacturer.
Tearing is 100% a matter of whether your video drivers are tuned for benchmarks or desktop use; just set an environment variable.
Not in my experience, it ends up working some places and not others and will also stop working intermittently. Also stuttering, flickering, artifacts... these just don't happen on Wayland for me. It's the smoothest desktop experience I've ever had, and that includes Windows, which, to be fair, is a low bar.