I don't think I have seen a USA so don't know if it is drilled or not. As for differences, these are all basically the same gun. You don't indicate what you want the gun for. If on a boat or for a beach house, you would want something resistant to corrosion (Mariner type), but then forget anything else. If you are not around salt water, you can get by fine with any model that otherwise suits your needs.
You seem to be looking for a defense gun, so a short barrel and extended mag are good ideas. If you already have a good hunting shotgun with a 5 round capacity, I would look to just getting a short barrel for it rather than buying a new gun. Your choice.
Any suitable shotgun can be drilled for ghost ring sights, which sound more impressive than they are anyway.