I think each of them give the gun an incremental power up or something. The thing is, you can unlock the same incremental powerups through the multiplayer mode when you spend in game credits to buy packs that have random stuff in them. It's similar to buying Pokemon cards or whatever. So these upgrades are likely in the full release.
The N7 edition has all the DLC except for one gun you get for getting the game from Origin.
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Gamertag/PSN-Murphiroth