I think two is probably a bit much.
Will definately have two when I get a small holding.
I have a lone Pilgrim gander who free-ranges along with one male Ancona duck. They seem to get along just fine. Neither of them is fond of my pet turkey, though. They are pretty indifferent to the chickens (who are supposed to be in their pens, anyway.)
My gander is very quiet. He would probably honk if we had visitors except the dog barks so much, his contribution isn't needed.
I have a single goose (3 months old) in with a flock of 7 ducks. She does just fine with them, but she rarely ever grazes - nowhere near the 90% that she should be. My goose does NOT leave the flock to go graze by herself. The only time she grazes is when my ducks are out bug hunting. She acts hungry quite a bit of the time and is always begging for food, which is why I am working on getting a friend (or actually TWO) for her. It is possible to keep a goose with a flock of ducks, but IMHO, I think the goose would be happier with other geese.
My Chinese goose and Blue Swedish drake are best friends. They scream in panic if the coop door closes between them for a second. I was going to get a companion for my drake by I couldn't do that to my goose now. I can't imagine a better pair. The goose is VERY protective of my drake, she gets between me and him if I try to pet him.