Finally, after a 3 day weekend of going through an re-tagging all my Music (Just Artists and Albums, no Soundtracks or Mixed Compilations like Billboard Top 100), here is what I got.
1. Re-tagged all Music using MusicBrainz Picard 1.4 using ID2.4 and removing all other tags, with these add-on's (Remove Feat. Artists in Titles, Last.FM Plus - the fixed version listed in the forum).
https://picard.musicbrainz.org/plugins/
2. Added the @DaveBlakes changes to add AlbumArtists in Picard ($setmulti(albumartists,%_albumartists%).
3. Added a new Artist without any Artwork or info (so just the tagged info, and the cover art supplied by MusicBrainz Picard).
So my results...
A. Because I have a large library, it took over 30 minutes to remove all the existing Music, and do a library clean.
B. Importing the "New and Improved" Library took nearly 4 hours.
C. Then end result, nearly the same as the original. 1400+ Artists with the "Show Song and Album Artists" turned "ON", and 759 Artists with it turned "OFF", so not really any change.
D. I did add a few new Artists without artwork for testing Album Artwork, and this worked, so that's cool. This is what probably bumped up the Total Artists. I also noticed when doing the new Picard scans, that some of my Artists had Sub-Artists in their folder. For example INXS had an Album from Michael Hutchence (lead singer of INXS) in that folder. Probably should have moved that out separately but I didn't at this time.
E. There were no more MusicBrianz ID's for Artists names. But there were plenty of Artists that were in my list, before turning "OFF" Show Song and Album Artists" that had no Artwork or info (other than the fact, they were part of another song, from another Artist on my list). If I turn on "Download additional information during updates"
F. I'm not really sure what ALBUMARTISTS effect (if any) had on my Music Library. Nothing I can see, but perhaps there is another setting I need to turn "On" to see something? I believe this is kinda what the Script to remove Feat. Artists from Track titles does (so for those people who don't want that add-on in Picard, Kodi can do it with the "Show Song and Album Artists" feature (is this correct)?
G. Next up, is to import my Various Artists (Compilations) which are in a separate folder than my Music, and see what the effect is. I'm guessing with turning off "Show Song and Album Artists" that I wont see any of these Artists that I don't have artwork for. But they should all show up under Various Artists as they are tagged that (ALBUMARTIST is Various Artists), and it worked correctly in previous versions of Kodi (fingers crossed). Let me know if there is something special I need to do within Kodi to get it ready for adding these.