What defines an album on a computer is a very different concept from a physical album such as a record or a cd that is one item.
On your harddisk there are no albums. Only files. (songs)
(unless you have a whole album as one single file, but that's rare)
So the music player/manager software you use will have to sort out what it's user considers to be 'an album'.
It can be that all music files that reside in the same folder are treated as an album.
Or it can be that all files that have the same Album Title and the same Album Artist are treated as an album.
With MusicBee, you can decide and refine all this to your own preferences.
So, long story short: Custom tags are always for files, never for albums.