Flux is considered a good quality group so I would go for that one: https://trash-guides.info/Sonarr/Sonarr-Release-Profile-RegEx/

Edit: just realized that ntb is also in that exact list. In that case go for the highest bitrate for better quality. Thus the flux one.

Isn’t Mullvad considered a bad option now since it doesn’t allow port forwarding anymore? It still works in my setup but I thought that being able to portforward increased potential peers?