Hi
If the playback is in full HD with no issues on your local nachine using VLC etc, the output seems to be correct.
As Mylenium pointed out, YT *playback quality depends on a number of factors e.g your bandwidth speed, if the vid has been cached on the YT servers etc.
Can you share a Speetest result with us.
You can do a test here and then screenshot the results:
https://www.speedtest.net
Post your dowmload and upload speeds e.g
Mo
... View more