That really depends on your threat model. The app isn’t monitoring your activity or has imbedded trackers. It pulls content directly from YouTube’s CDN. All they (Google) know is your IP address, but nothing else. For 99.9% of people that’s totally ok.
There are several way, honestly. For Android, there’s NewPipe. The app itself fetches the YouTube data. For PC, there are similar applications that do the same such FreeTube. Those are the solutions I recommend.
If you’re one of those, you can also host your own Invidious and/or Piped instances. But I like NewPipe and FeeTube better.
Pretty much. It’s pretty straight forward.