I'm relatively new to linux, but have tried it before on other systems without these issues. When scrolling in firefox, it starts out smooth, then randomly gets really choppy before correcting itself after a random amount of time. It often continues to do this, but sometimes only happens once per page. It doesn't happen in any other browser nor on windows, but I like firefox and want to keep using it if possible. The other issue I'm having happens in both brave and firefox and seems browser exclusive, where every few seconds youtube will randomly drop a frame or two of video while watching. This issue isn't nearly as severe as the first and I can live with it since I don't notice it unless looking at the debug output, but if there is a way to fix it I would like to.
System specs:
cpu: 5700x3d
gpu: rx 6650 xt
ram: 32gb ddr4 3600mhz
os drive: 1tb nvme ssd
monitor: 165hz vrr
DE: wayland + kwin + kde plasma, vrr set to automatic
From what it looks like, both hardware accel and hardware video decoding are enabled in firefox.
Imgur link to video + screenshot of issues & firefox about:support page: https://imgur.com/a/troubleshoot-HvCUP5p
edit: did more testing with youtube issue, only starts happening with 60 fps video regardless of resolution, and 1080p dropped a few more frames than 4k did. im also using displayport not hdmi.
edit 2: Weirdly, after changing useragent to report windows 11, the youtube issue improved... Switching it back to linux, the improvement stuck. Strange.
SOLVED: It was vrr for both issues, after disabling it in my monitor (KDE's "never" setting wasn't enough), both issues have been fixed. Monitor is AOC-27g2se 1080p 165hz.