> AVIF is basically the keyframe format of AV1 video, with a bunch of still-image-specific optimisations thrown in. Animated AVIF however, is pretty much just a repackaging of AV1 video. You can convert an AV1 MP4 to AVIF and back losslessly - it's just a container change. That's why it performs so much better, because it's built for motion.

So, is animated AVIF only keyframes / p-frames, where each frame is independent from the other? I was under that impression, uncertain if there are any other capabilities it might have (like only updating part of the canvas when only parts change, like GIF supports)

No. I used to think this too, but it isn't limited to keyframes.You can convert an AV1 MP4 to AVIF and back losslessly - even if it has non-keyframes. It's just a different container. It has the full AV1 capability. Plus transparency.