I would be surprised if this was related to the GTK issue because GTK was never as dramatically fast as `MOZ_ENABLE_WAYLAND` seems to be. Maybe Firefox exacerbates the issue as you say, but either way it feels like Firefox needs its own unique fix. Please don't just wait for a GTK fix and expect that to also fix Firefox.
I would be surprised if this was related to the GTK issue because GTK was never as dramatically fast as `MOZ_ENABLE_ WAYLAND` seems to be. Maybe Firefox exacerbates the issue as you say, but either way it feels like Firefox needs its own unique fix. Please don't just wait for a GTK fix and expect that to also fix Firefox.