1). It doesn't go up from 100%
2). I was adjusting it with the scroll, very easy to use, now that doesn't work either. Windows 11 25H2 Updated.
WaterFox 6.6.10 And Firefox 149.0

It seems It could be both Twitch and YouTube that aren't working with it properly, where going from 100% to 120% sounds like going to 200% instead. 1fexd version defiantly still increments up less at each 10%