I tend to only listen to youtube videos and only cast them when I want to be able to see the images, since I mostly watch history videos.
I did notice the other day that with an iPad I can select 1080p, which is perfect! I’m not sure what exactly is causing the difference, maybe youtube sees safari on an iPad as different somehow, but that’s solved my one little issue I had.
Are you able to cast at 4k or 1080p? I used to have youtube premium but moved to the same setup on my phone; ad blocker, sponsor block, youtube mobile, cast to tv. My one issue is that the youtube player only lets me select up to 720p for stream quality, and that doesn’t look fantastic on a tv.