Tbh, I feel like this was a genius move by Apple. AirPlay’s 2 second delay gives plenty of time for all devices to sync up and they simply build it in to the AV playback so that videos are perfectly synced to audio as well.
However, without that source-side adjustment: 500ms is a lot. Especially for video.
Yes, snapcast is really designed for audio streaming. For video it's not going to work (but surely for video cases you want something to stream both audio and video?).
However, without that source-side adjustment: 500ms is a lot. Especially for video.