Apple Music files & iMac and iPhone synching

I've had a couple of questions for a while, and I'm not sure if it's possible to solve them.

I'm a member of an Apple Music Family subscription, but I'm not the owner.

I have a late 2015 iMac and an iPhone SE (2nd generation).

I have a ton of music on external drives. I'm very particular about how I name and categorize music files in Apple Music. I don't want to lose my file-naming conventions, etc.

I use the Finder > Music > Playlists section to sync music via specific folders and playlists onto my iPhone. I use the Selected artists, albums, etc. button to sync.

In Apple Music settings, I have deselected Sync Library. The reason is that I don't want Apple to overwrite my naming conventions on my phone, and I don't want Apple to eliminate my playlists and playlist folders in Apple Music on my iMac.

Question 1: Is there a way to sync my library to the Cloud Music Library without Apple eliminating all my playlists and naming conventions? I've clicked Merge before, and Apple Music completely wiped away my playlist folders. I had to start rebuilding folders and playlists from scratch.

Question 2: Can I add Apple Music songs to a playlist on my iMac without synching to the Cloud Music Library? I would like to create a playlist folder of new music that I'd like to add from Apple Music. I'd like to sync this folder between my iMac and iPhone. But every time I try to add music from Apple Music to a playlist folder on my iMac, I get this dialog:

I hope this makes sense. Essentially, I'd like to sync Apple Music files to one folder without letting Apple rename my entire music library, playlists, and playlist folders.

Question 3: Is it possible to sync my library on my iPhone only? That might solve the problem, as long as I can create a playlist folder on my iPhone. How will selected Sync Library on my iPhone affect my files in Apple Music on my iMac?

Any help appreciated! Thanks.