I this isn't specifically a SideQuest support issue, but what I would say is you don't really need to be playing 8k videos inside a headset where you'll never be able to see the benefit of the 8k (unless they are 360 degree videos) , the screens are the limiting factor here. I would suggest only needing 2k or 4k at the max in resolution of the videos. I would also suggest using bigscreenVR as it has a video player and a youtube player that has been added not too long ago, so just drop the files onto your quest 2 internal storage, or stream them from your network folder.

I hope this helps!

BOB