Just to clarify, you won't get everything if you get the CE. There are quite a few DLC that are not included in the CE.
There are also way, way more than 3 DLC. You are probably thinking of the "Theater of War" (ToW) DLC. Those are single-player and co-op mini-campaigns.
In terms of DLC, there are the ToW DLC, vehicle skins, faceplates (which affects the loading screen for multiplayer), and commanders (which are like the doctrines from COH1). There are a lot of these.
I got the regular edition and bought other things piecemeal. The CE is great if you want some of the ToW content, a whole bunch of cosmetic customizations, and some commanders (some of which are good, some of which are redundant. None of the really controversial ones are included).
