Huh? I use YouTube all the time on Firefox and it's fine. Better than fine, really, thanks to the YouTube improvement extension I have loaded. Never heard of the other two though.
Google is essentially using A/B testing methods to slow it down for one group of FF users while keeping it absolutely fine for another. Funnily enough, I've been placed in this 'slowdown' group even though I am a Premium subscriber ever since it launched (post-Red renaming) and another channel on the same Google account has 0 issues in the same browser on the same PC etc.
