Syncing few kodi instances with MySQL on a NAS – issues

Hi

I have few issue that I would like to get assistance with. This for syncing few kodi instances with MySQL on a NAS.

My setup is as follows:
I have 2 RPIs running Kodi 17 and a third installation of Kodi 17 on android device.
My movies and music libraries are on a NAS and this is where the MySQL is installed.

All kodi instances have the same advancesettings.xml.

I had to drop the databases myVideos107 and myMusic60 from MySQL so these will be recreated, so I shut all kodi instances and started only one, then started library scanning process.

1. Now, I have noticed that in databases folder in the running RPi, the MyVideos107.db and the MyMusic60.db were not created. How could that be? I thought it should have created those when the tables in MySQL have been filled with the information on each of the Kodi instances.
2. I found out that after scanning, the movies somehow already include the information of watched, unwatched, and resume in the case movie started and stopped in the middle. Where did it get that info from?

The third issue is about the thumbnails. Should I copy the thumbnails folder from one RPi to the other instances? Or it is copied automatically?

Regards