I'm not sure if this is Firefox related, but I believe it is.
I use Budgie version of Solus and Firefox has like frame-per-second spikes... Every 4-5 seconds the Firefox gets stuttery, I can see that when I keep scrolling a web page for example. It's like the frames drop, it lasts for about 2-3 seconds.
I tried disabling hardware acceleration.
All updates are installed.
I don't have this problem on my very weak laptop. (But the laptop runs MATE version).
I did not notice any FPS spikes in video games. (Only lower performance compared to WIndows, thanks to the open drivers).
Also when I was downloading a file through browser, the computer became almost unresponsive. Firefox was using about 80% of 2 cores of my CPU, sometimes it jumped to 100%. But it also happened when I had only 3 tabs opened, not downloading anything... 2 of those TABs were just YouTube videos.
My hardware specs are:
AMD Radeon R9-280X 3GB VRAM
Anyone else have something similiar? Firefox version is 58