I don't have experience with buffs being with other geese, but I would think it probably wouldn't be too bad.....I don't see them as being total pushovers....but dunno....could depend on the individual birds involved....
As for intimidating a predator or becoming prey.... I wouldn't put it past them to possibly attempt to intimidate one. Mine would like to attack our house dog, a terrier, if they ever see her outside....and while I've always tried to keep them away from one another at such times, the dog is intimidated and keeps her distance now, but if the geese got ahold of her I'm still afraid she would bite back in defense. lol
And while they act like they would like to attack a dog, they will sqwuack and run from my 4 week old chickens. lol I have seen them bite at a chicken before, but a sudden move and the goose will run....as will the chicken. lol