Out of the box it can play audio in the background, and now that extensions are available you can block ads as well. You don't really need constantly updating 3rd party clients or questionable firewalls anymore if you just want usable youtube on a phone.
Yes for all those things. Doesnt have youtube recommended or sign in, but you can export youtube subscriptions from your account. LibreTube is also great and i like it better (when my phone doesnt cause problems)