For YouTube, NewPipe is an anonymous…

Not quite. From LibreTube’s GitHub page on their differences:

With NewPipe, the extraction is done locally on your phone, and all the requests sent towards YouTube/Google are done directly from the network you’re connected to, which doesn’t use a middleman server in between. Therefore, Google can still access information such as the user’s IP address. Aside from that, subscriptions can only be stored locally.

LibreTube takes this one step further and proxies all requests via Piped (which uses the NewPipeExtractor). This prevents Google servers from accessing your IP address or any other personal data.

Either way, I use a VPN for both.