Should a Bandhelper sync also update the data on SetList Maker if they share the same database. I make the assumption that Bandhelper and SetList Maker will access the same database if using the same database name and password.
No, Set List Maker and BandHelper don't sync with each other. You can export your data from Set List Maker and import into BandHelper to do the initial setup of your BandHelper account. Then you would use the BandHelper app instead of Set List Maker.