Youtube offers everything as people around the world use it and Japan is slowly moving towards 8k.
After seeing all of this, I can confirm that you are seeing only 1080p and nothing more. You can play whatever you want, but that will only be more taxing for your internet speed and hardware as 4K is very taxing for CPUs. On my old i7 2600K, the usage used to climb past 70+ per cent.
