Is here a good place to comment? Giving it a go anyway.
Worth noting that basic album art (cover) can also be scanned from the appropriate tags embedded in the music files. That is where most of my art comes from. Then album and artist art can be scraped from online sources or NFO files with the location of the art, or manually set to locally held files.
Basic music Artwork
Having a folder for every artist on the compilation is a CDart addon thing, not out the box Kodi. Kodi will not do anything with such folders.
Worth explaining that the name of folders does not matter to Kodi at all, just the files located beneth then and how the music files are tagged
The artist folder is the folder that contains somewhere below it all the songs by that artist. Kodi finds it by searching for the lowest common denominator path (no idea how to say that in user language) not by looking at the name.
Likewise the album folder is the one containing all the songs on that album.
Worth discussing impact of having just one album by an artist, and disc sets. probably some more explanation in my comments on import
My References http://kodi.wiki/index.php?title=Artwork&oldid=81191