How can I avoid syncing of photos between iMac and iPad?

Thanks for your reply.

I have checked and rechecked, and not one other album is checked to sync. Nevertheless, the only thing that happens when I hook up the M2 iPad Air running iOS 18.3.1 to my M1 iMac running MacOS 15.3.1, it that, although nothing is checked besides " _SyncOnlyThisAlbum", all my photos ( > 20000) start transferring, until I pull the plug.

I have meanwhile also checked my two other  devices: iPhone XR also running iOS 18.3.1 and iPad 5Gen running iOS 16.7.10: neither of them has any option checked on the photos tab and nevertheless: both behave as they should: No syncing without my intention.

Thanks, Zurarczurx, now that is something I am definitely going to try out. You see, I'm a lot more familiar with Mac than with any of the devices, including the one that's now giving me the most trouble. That was a present from my wife for my 75th birthday, which is tomorrow, so it might take a couple of days before I do this (there's some mild partying to go through first). I can use the new M2 iPad without hooking it up to the Mac, and I will surely report back what the result was. You are very careful, but I'm almost sure I can do the things you suggested with little or no trouble, unless -perhaps- that the two  devices that behave themselves now, might start acting up once I've dealt with Finder's plist file and probably others as well).

The M2 iPad Air happily starts synching, and I, quite unhappily pull the plug.