Don’t get me wrong, I use Beets for my entire library, but it doesn’t solve any of the issue OP has. It does not get metadata from streaming sites or anywhere else, but same as Picard from Musibrainz. It does not allow to manually change metadata of music you are importing. On the contrary, for that Picard is the better tool as it allows that.

There are not many advantages of using Beets over Picard, apart from CLI, and especially for the OP use case.

Beets is great but it also uses musicbrainz so won’t really help OP.

Ubuntu -> Manjaro -> Arch -> Gentoo -> NixOS

I recently switched to nixos which makes dependency management and configuration itself much easier. Probably the best option to run things on bare metal IMO.

Sounds like Windows rewrote boot manager. It likes to do that sometimes. Basically your only choice is taking live USB booting into it and reinstalling grub.