Start your stream on YouTube first, then connect. Works on your own website (gxbdgaming.online); this preview page blocks Google's servers. Reading chat uses your API quota, so the check runs about every 8 seconds.
Demo chat turns off by itself when YouTube chat connects. Don't leave it on during a real stream.
All music is created by the game itself while it runs, so there is nothing to copyright-claim. Browsers need one click before sound can play; OBS usually plays it straight away.
Press H to hide the Stream settings button for a clean capture. In OBS, add this page as a Browser Source at 1080 × 1920.