Hey again! I did read the question, I believe backing up data is just part of the syncing process, but if you didn’t want that to happen automatically, you can change the option I posted earlier.
You can, if you need to, disable iOS backups all together using Terminal, which I’ve done. I don’t recall for sure if it affected the syncing process, but think that function remained working okay.
There are other programs you can use as well, if you don’t like the way iTunes/Music operates anymore, although, if you’re like me, that can be a tedious process, and personally don’t have an issue with the backing up part.
In fact, (Unlike it used to be), now when you do a backup, it replaces the previous backup with the newer one, taking less space on your hard drive, (I believe unless you re name your phone, or reset the settings). Good luck.