Is it possible to force Plex to use only my metadata?

I disagree. All of my tags are clean & succinct & organised in the way you describe.

In my first thread on the subject (& I apologise for repeating versions of the same question but the threads seem to die & people stop responding) I’ve shared a couple of screenshots of my hierarchy.

It’s very clean &, as far as I can tell, adheres to each of your conditions (apart from the composer one. I use the composer field in my classical music, but I can easily remove it & add the composer to the beginning of each track. I mean, it’s a lot of work, but it still makes sense to me to do it that way, as I already do that with albums that have more than one composer.)

In any case, I don’t need support for a composer tag because I’m wanting to organise by album artist & the album artist tag is correct & there is most definitely only one for each release.