My questions are: If I have 10,000 files, would I have to split them into 2+ document libraries, but they can both be synced to the same OneDrive for Business?
If I have 30,000 files, does that mean that I will need 6+ document libraries and I would not be able to sync all 6 to one PC via the OneDrive for Business?
You can sync up to 20,000 items in the OneDrive for Business library, including files and folders.
5,000 items in site libraries, including files and folders.
Also, is there a way to see how much is our storage usage? (used/total)