Glad you had a good experience with the music matching. I didn't - Apple Music replaced (and kept on replacing) some of the tracks that I really like with completely wrong replacement tracks - and no way to tell it to make an exception for those tracks.
It was pretty for that reason that I stopped using AM.
I’ve had some problems with it in the past, so I sympathize. It’s not perfect. I wish they’d get rid of matching, or let the user flag tracks as “do not match”, and just upload everything instead. This is what I liked about Google. It lets you upload your library but it doesn’t match anything. The problem is, there’s no desktop integration so managing your music becomes a manual/tedious process.
Before returning to AM, I manually went through my entire library and made sure everything looked good, no dupes, tracks properly tagged, etc. And then I made a backup pre-upload in case AM screws something up. I’d go back to Google in a second if they provided iTunes integration or worked with a third party app like Swinsian.