If it's like, mostly a still background, AV1 might be able to keep it crisp at 1080 in that size. But if it has more going on then yeah it would probably be too heavy 720p should be guaranteed to look crisp without too much CPU time, but maybe load faster with more CPU time 480p should look as crisp as 480p can and load easily without much CPU time I think nostr.build might be able to do video compression too, they were at least talking about rolling it out