[itsme]

Here's how I manage a pretty similar situation (see screenshot):
In MSP I manage the files myself
d:\HerbertsGoogleDrive\_MobileSheets\ is my MSP storage location
d:\HerbertsGoogleDrive\ is synchronized by 'Google Drive for Desktop'
Almost all sheets that I use on stage are 'one file per song' chordpro files or PDFs exported from ChordPro, MuseScore, ABC or Finale. They are in the subfolders of _MobileSheets\Songs\
A number of essential songbooks that I want to carry around all the time for sessions, practicing and rehearsals are in _MobileSheets\Fkbk0\
These two folders are maintained in my main mobilesheets.db and synchronized to the tablets that I use on stage.
On my notebook (where storage space is only limited by the 15 GB of the free GoogleDrive) I have many more files and several separate MSP databases to keep track of the whole collection, hljpa.db for the Hal Leonard Jazz Playalong series, MSPTest.db for test purposes and a really big one for everything.
A great feature of MSP: if all paths are relative, the MSP databases are compatible and can be copied easily between Android and Win10 devices.