It's hard to find a mellow German Shepard! Bred to be guard/ working dogs, and MUST be trained! Many are neurotic, poorly bred, and difficult.
The right Doberman might work. Again, trained, socialized, and a guard breed.
Retrievers vary: Goldens, lotsa hair, mostly mellow. I have met a very few biting jerks, but not many.
Labs, as i said, either busy or laid back. Some guard.
Chessies, all guard, great if you can train and be IN CHARGE at all times.
Haven't dealt with too many Curly Coats, don't know about them. A fairly rare breed.
Mary