Database issues in multiple version of Kodi in android box.

Recently I have upgraded my media box from WDTV to an android box with Kodi.
I have three different versions of Kodi in my android box!!!

1. Manufacturer’s version of Kodi similar to SPMC
2. Kodi Jarvis 16.1 on Android 5.1.1
3. Kodi Jarvis 16.1 on LibreELEC.

Initially I was not sure which one to use… and finally decided to use the 1st version.

I loaded my offline movies collection from a Western Digital My Book 4TB HDD formatted as NTFS connected to the Kodi box. Everything is almost OK, except some very few movies on the HDD have not appeared on the library. I am trying to troubleshoot this problem… Any tips?

I still have other data like offline TV shows, Music and Photo collection on another Seagate 4TB hard disk (NTFS formattted) to load on Kodi.

Now my question is, Should I add everything on one Kodi application? If so all these media files may create a larger database and load up the system. Will this affect the Kodi’s performance? Also if this Kodi crashes for any reason, I have to redo all of my media again.

If I use any of the other two or both Kodis (remaining Kodi versions on the box) for the second hard disk for load sharing, will this improve the overall performance of the Kodi box?

Another question is by using two or three different kodi versions on one box, will there be different library databases for each Kodi or a common one. Logically they should be different for each Kodi version. If so is there any problem in using multiple Kodi versions on a single box.

Finally Can I use the existing Kodi 16.1 from manufacturer (until he updates to 17) along with another Kodi 17 updated from 16.1 on android (2nd option above), will there be any compatibility issues?