Good vault stories usually involve complex social structures within the vault. Take Vault 101 from Fallout 3. There was a strict isolationist policy, and the main character had to deal with the rules and the people who enforced them. The relationships between the different factions within the vault, like the Overseer and the rebels, add depth to the story.
In Fallout: New Vegas, Vault 22 has an interesting story. It was a vault where they were conducting agricultural experiments. However, things went wrong as mutated plants started to take over. The exploration of this vault reveals a lot about the hubris of the pre - war scientists who thought they could control nature completely. The remains of the vault and the mutated plant life make for a spooky and thought - provoking vault story.
Yes. It can be very significant. It might be a place where the secrets of the Peverell family are stored, and since the Peverells are related to the Deathly Hallows, any secrets there could change the understanding of the wizarding world's most powerful magical items.
Vault is purely fictional. The story and characters were made up by the author's imagination. There's no connection to any real-life incidents or people.
The Vault is more likely to be a product of imagination. Usually, such elements are crafted to build an engaging narrative rather than being based on real events. There might be some inspiration drawn from real-life situations, but it's not a direct reflection of a true story.