No problem.
The following isn't really in answer to your question, which I've answered the best I can, but I started thinking with my keyboard, and it seems like it might be informative to someone, so I've left it here.
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There are basically three kinds of music tracks in iTunes.
1) The tracks you import. Apple does not own or control these, they just let you import them so you can play them through iTunes and Music on your computers and devices.
2) Music you've purchased from iTunes. In theory these are yours (only and always yours) to enjoy forever. However, nothing is perfect and some tracks occationally disappear from iTunes. This does not effect the songs you've already downloaded, but it does prevent you from re-downloading them if you happen to lose your local copies. These, in theory could be taken away from you. I don't think Apple would ever do this, at least not willingly; but the future is never a sure thing.
3) Apple Music's streaming service. An all you can eat service, everything in the iTunes library is yours to listen to, so long as you keep up your subscription. You can't really call this holding your library for ransom, because it's never your library in the first place. It's their library, that you're paying to access.
The import options is the oldest, and how those of us who started with the orginal iPod's started our libraries (there was no iTunes Store). In theory, these songs are safe from deletion. They are legaly yours (so long as you do not lose the original media or license). In practice, iTunes can sometimes replace them with tracks from the iTunes store. This was what the original iTunes Match did, in order to make them more streamable and easier to sync accross devices. Well intentioned, it occationally lost the original track in iTunes.
My recomendation is, if you want to use iTunes and Music to sync and play your non-iTunes music, do so. It's a good player and service. But also keep a copy of your original library somewhere else, preferably on a different computer or disk drive. That way if something happens all you have to do is delete your iTunes library, and re-import. Or if that becomes unacceptable, there are other apps and services you can migrate to.