Dude, I have YouTube music and I literally am not able to change or upgrade to YouTube premium. They don't let me, it links me to a useless empty page with no options. I don't even know what the price is like. This whole subscription thing is a mess.
I solved it by using YouTube revanced and have all premium functions and more. On desktop I wrote my own player. It's so much better because their website is a mess. At this point do I really want to pay for features I know I won't use?
Just a shot in the dark here, but do you have ambient mode enabled? (that annoying glow light around the video). I've read from various people that it can use an insane amount of cpu on some devices. Disabling it fixed the performance issues they faced.