Buffs are a very calm breed, my Toulouse are a bit more temperamental than my buffs so I would suggest buffs, they’ll be more tolerant of your ducks and chickens.
Definitly get more than one, they can be girls or ganders or a mix of both, they’ll get a,omg with each other regardless. Ganders will sometimes squabble in breeding season but will otherwise bond with each other just fine.
If you’re not prepared for gander horomones two girls will do just fine, though they can be bullied more easily by drakes. You wouldn’t think it because they’re so much larger but sometimes my girls get bullied by delusional drakes.
Geese can deter hawks because of their size, but that’s as far as it goes, though they look large and imposing geese are very fragile and can’t realky defend themselves from predators. They’re best a scaring away hawks and humans.