Well, given the subject here, it seems relevant to ask how everyone is organizing their libraries in Calibre. Is there such a thing as "best practices"? Would really love to hear ideas as I've found library mgmt in Calibre to be cumbersome, sluggish, and rather none intuitive compared to something like Plex for movies & TV shows.

Check out Calibre-Web (https://github.com/janeczku/calibre-web/). I'm only mentioning it because you've mentioned Plex, because it comes with a theme that's a clone of Plex: https://github.com/leram84/layer.Cake/tree/master/caliBlur