I've heard/read that they're a good addition to help with predators.
They're sort of like roosters. Loud alarm systems, but they're probably not going to chase off anything bigger or fiercer than a small-sized dog.
I've also read that it's best to raise them together in order for them to get along well. Our feathery family will be a year old in March. Is it too late to introduce them to one?
The problem is that geese are quite capable of defending themselves, but by the time they get to that point, they're usually big enough that if they don't like the chickens, they can cause some damage. So you're not going to be able to just toss a baby or adult goose in with a lot of chickens and expect everything to go right. You can introduce them, but you'll have to have a strategy. And I wouldn't get just one; geese like other geese for company. I would get two, preferably female, because they're less likely to be human-aggressive, and they're quieter.
If we do get one, is it best to get goose young?
I would. Geese are some of the friendliest animals, if they're hand-raised. And that way, you can raise them beside the chickens, in a see-don't-touch pen.
All that said, Geese are loud. This is somewhat variable by breed, but a goose can be just as noisy as a guinea if he's in the mood. They produce poop easily twice the size of a golf-ball, on a regular basis, and they can shoot it out several feet. They're playful, and can be pretty destructive to a garden. They will eat cabbages, young corn plants, lettuce, brussels sprouts, beans, etc. And if they don't like the taste, they might just rip it out and leave it lay. There are stories on here about geese taking apart waterers, ripping up boxes left in the yard, etc.
https://www.backyardchickens.com/threads/goose-shenanigans.1340716/