I have like 4-8 skipped frames every second if i watch a 120fps stream or video on twitch (yes they exist), turning Hardware acceleration off works but i am hoping for another solution. Tried it with a fresh install (and deleting everything in appdata of course) of Firefox and Firefox Nightly but both have the same problem. I don´t have this problem on Chrome but i like Firefox more but i just can´t use it right now if this is not fixed...

Funny enough, when i start firefox's troubleshooting mode i don't have this problem, i don't know if it disables Hardware acceleration but in the Settings it's still enabled.