Safari 12: how to sync tabs *only* across devices? Is there a way to sync opened tabs only (i.e., without syncing Favorites page) in Safari across Mac and iPhone? 

I have a different set of Favorite websites on iPhone and Mac — and turning sync on for Safari overwrites them.
You can assign another folder for Favorites (e.g iPhoneFav).

I haven't tested whether this option will be synced across devices, though.