[Milhouse]

Are there any steps you'd suggest before I nuke Thumbnails, Textures and MyVideos (aside from saving copies to an offline location, just-in-case) ?

I guess the usual suggestion might be to export your existing library but that might make matters worse (not to mention using cached artwork). The main thing is to ensure you have your artwork present and named correctly when scanning, so make sure that's done first. Going forward you shouldn't really need to change your artwork, other than with the addition of new artwork using various tools (AD, mklocal.py etc.). Removing or renaming artwork should not be required, and if any tool is doing that you need to understand why.

Is this where I dump AD, and rely on Artwork Beef alone ?

I use AD, but only for movies and only for specific artwork items (clearart and clearlogo), and never let it write into my file system.

Is my real friend going to be a Kodi-friendly media manager ?

I use Ember for movies (quite an old version, 1.3.0.20 - haven't felt the need to upgrade), and SickRage for TV shows, and haven't had any problems.