If you only want to update a single tag you can add the list of tags you don’t want to get changed in “Options > Tags > Preserve these tags …”. See the following post for details:
If you have your files reasonable well tagged, and it looks like you have, you should always use first Cluster and the Lookup to find the album info on MusicBrainz. This will usually give you the best results.
Use scan for difficult cases, e.g. wrong or very incomplete / missing tags (e.g. titles only “Track 01”).