and it comes with a streaming music service that I personally believe is better than Spotify
On desktop I'd never notice (I haven't run without an adblocker for probably ten years), but on mobile it's a sanity saver.
Not in my experience - and I use the mobile app daily (my lunchbreaks generally consist of catching up on the few folks I subscribe to).
I also haven't noticed any sort of push towards YT Music...But then again, I don't really "browse" Play Music either; I just press play on one of my previously found artists (using the Start Radio button) or search if I'm looking for someone I've not listened to before.