From the handbook:
"All the scores should have the same number of parts and staves for this to work correctly, ideally with the same instruments in the same order. If the scores have the same total number of instruments but not the same ones, or not in the same order, then the instrument names from the first score will overwrite ones from subsequent scores. If some of the scores have fewer instruments than the first score, then empty staves will be created for those sections."
Comments
From the handbook:
"All the scores should have the same number of parts and staves for this to work correctly, ideally with the same instruments in the same order. If the scores have the same total number of instruments but not the same ones, or not in the same order, then the instrument names from the first score will overwrite ones from subsequent scores. If some of the scores have fewer instruments than the first score, then empty staves will be created for those sections."
See:
https://musescore.org/en/handbook/albums#join
To create an album of various types of scores, consider the Album Manager:
https://musescore.org/en/handbook/albums#create