First up, I always get author and title from file name, and I make sure I have those as I want them before I add a book.
If I am adding one or two books to a library - which is mainly true these days, I don't use an intake library. I add them, one at a time, to the relevant destination library. I can usually fill in most of the metadata blanks via copy and paste from an existing book by the same author. I also have my workspace arranged so that I can see any metadata notes I have previously collected for the 'book' in the xplorer˛ preview panel.
Occasionally I add dozens of journal articles or media items, in that case I create an empty intake library by cloning the destination library and I might seed the intake library with some books from the destination library to copy from.
I could colour them via your VL from IDs JobSpy trickery - I have to be careful not to change them or copy them back.
I tried and failed to devise a way to get a universal intake library that would cover my different libraries. When Kovid provided metadata copy & paste… perhaps at my request… the need for it diminished greatly.
FTR: I don't read series or fan-fiction (not sure I even know what it is), I don't download tags or ratings, nor do I care much about covers and comments.
Added: and I dont use any device integration - I only keep a few things on my phone and I prefer to manage that myself, ditto my Surface GO.
BR