Call of Duty®: Modern Warfare® II

You would get the items that are listed on the store page that come with the vault edition.

yes but Warzone 2.0 uses the API base game COD MW 2 so if you activate Warzone 2.0 automatically COD MW 2 which is in your steam account library, and if someone makes GA COD MW 2 in SG you cannot enter it because it will be seen by SG that you already own the game