[Blindedwino]

Sadly, FF still slows to a crawl on OSX and it makes it unusable for me. I can't even watch a Youtube video without it skipping frames.

[micwag]

Try h264fy: https://github.com/erkserkserks/h264ify-firefox It forces h264 on youtube, which is HW-accelerated

[blauditore]

That sounds like graphics drivers issues to me; I would double-check that.

[Longhanks]

Unless you're running a Hackintosh or a customized Mac Pro, there's no such thing as a "graphics driver issue" on macOS (if the rest of the system works fine).