I have edited some earlier posts that you might have read already.
When I wrote message #1, I had not yet done what is described in post #2.
Post #3 explicitly references the attachment to post #2, and implicitly post #1.
Post #1 is still valid. I just migrated my Pristine Library to Q&S and renamed it just as is described in the attachment to Post #2.
Having a huge library is a game-changer due to the enormous clock time required to copy/move books from one library to another (hence the attachment to post #2).
The posts (click to view):
(Post #1)
Multiple Q&S Libraries and Synching Tag & Title Rules
(Post #2)
How to Swap New Q&S metadata.db for Old Standard Calibre metadata.db
(Post #3)
Definition of a "Pristine Library"
DaltonST