Go read the Help: FAQ (kinda late on NAS/Cloud storage)
GD is known to be 100% incompatible with a Library (file structure)
(AFAIK You can Zip up your Library , The STORE that as a backup)

Every (new) user should absolutely read the FAQ before installing or changing things outside of Calibre.
Be wary, of the MR posts that say 'Works fine for me'. Some issues are listed because they are unpredictable. They are known to fail, just not when it will happen.
Calibre EXPECTS a local attached (internal or USB) drive and NO 2-way sync