So I tried the app. Looks really well done. Just wish Plex didn't have to pull metadata from online. Looked in all the settings and can't find anyway to turn it off. Really wish they would let me just use my own metadata and cover art. Deal breaker for me unless someone knows something I'm missing.
You vsn use whatever user agents you want in any order you want, or totally edit all the pulled in meta data from the sources you specify in the order you specify till your hearts content. No idea why you want to do it all manually from scratch though, what a waste of time!