Just tried it, setting gfx.webrender.compositor.force-enabled to true made firefox unusable with all sorts of visual glitches so I changed back both.
Kinda annoying. Somewhere a month ago firefox suddenly turned sluggish. It loads fine, video playback is ok as well, but the UI animations on the video player like seeking, changing volume, subtitles or video speed are really laggy.
I switched to a completely new profile and tried disabling all of my extensions but it's the same. Kinda accepted it at this point and am ignoring it. It came out of the blue hopefully it gets fixed as well.