iPhone to iMac Sync Removing & Re-Downloading My Music

I have an older iPhone 8 running iOS 16.1.2 and a newer iMac running Ventura, 13.1. Everytime I sync my iPhone, it appears to remove and then re-copy the selected playlists I have chosen from my iTunes music library. This takes considerable time & seems repetitive. On top of this - the iPhone sync Finder window dialogue doesn't seem to notice specific iPhoto folders to sync - rather only offering the option of syncing "All Photos." I feel these may be related to my syncing problems and can't find any solutions on-line. Looking for any suggestions.