Using multiple music libraries separately while having an Apple Music subscription

Hi,

I'm having questions about multiple music libraries, having never used this feature before. I'm a long time Apple Music subscriber, but I also want to use my old 1st gen iPod touch with my own local files. There are doubles of music I added with my subscription among my files, so I want to create a separate library for the iPod to avoid messing up my primary subscription library.

Can I have both libraries exist completely separately and not have them share any data between each other at all? Will I still be able to keep using my primary subscription library on my current iPhone without any changes, cloud syncing with macOS and all? In other words, the iPod library only gets local files and no Apple Music, while the Apple Music library only gets subscription music, cloud sync and no iPod files, and the Mac can both cloud sync Apple Music with iPhone in one library and manage the iPod completely offline in another, all under the same account. Is this possible to do? Thank you.