I can't find where / how to sync via WiFi. By "sync", perhaps what I really mean is "backup" as in "Back up all of the data on your iPhone to this Mac". In iOS 12 and before, I could go to Settings => General and sync (which I took to mean the same thing as "backup" since there is only one date displayed).
Also, twice now, my iPhone settings on my Mac have reverted to backing up to iCloud -- which I wouldn't mind doing except that I don't have the storage needed for all my iOS devices and also my internet upload speeds are horribly slow.
Also, twice now, my iPhone settings on my Mac have reverted to backing up to iCloud -- which I wouldn't mind doing except that I don't have the storage needed for all my iOS devices and also my internet upload speeds are horribly slow.