Stop Video/Audio = stop buffering
Once media begin playing there is no way to stop/suspend it from buffering even when you STOP it. Currently, You can only PAUSE it from playing but it will keep buffering in the background, that's the most bizarre behavior for video/audio tag implementation in HTML5 (other than we can't stop any media from playing/buffering on-load).
So, I think there should be a default browser implementation to FORCE Stop/Suspend any video/audio tag on demand by user, regardless of the media player support for such feature. Just like img & gif, we should be able to stop 'em from buffering when we want to.
This userscript can stop some video buffering, not perfect but better than nothing: https://greasyfork.org/en/scripts?q=viewtube