I have a Surface Laptop 4. Watching YouTube full screen with almost nothing else running has the fan at high speed all throughout, and battery dead after 3h. I’m not even mad. It’s just sad.
Youtube defaults to VP8/VP9 encoded video that you most likely decode in software. Install h264ify chrome/firefox addon and it's likely going to get better.
All Intel CPUs since like 2016 have VP9 decode support; that's unlikely to be the culprit.