So I figured out how to play YouTube videos at 1080p using android or Remix OS; install YouTube app, do not use chrome or any web browser.
HDMI sound works with 1TB board.
My youtube app also only plays 480p videos. I don't know how to go about it.
I got a 2GB board running latest Remix OD (15/4/2016)
I'm also able to stream fluid 1080p videos with the YouTube App on Android. That was impossible with Chrome or any other browser.
I think this has to do with GPU HW acceleration.