PinePhone can play FullHD video at 60FPS on an external 1440p monitor (incl. the up-scaling to 1440p) smoothly, without breaking a sweat. So as long as the codec is something supported, like H.264, video is no issue at all.

https://www.youtube.com/watch?v=dHOgVmxH_dA

SW is lacking somewhat, still.

I just tested: Firefox is able to play reasonably well a Youtube video at 720p 25fps.