Ok, so I got my wraithguard the proper way and did the job on Dagoth. But there seem to be at least two more wraithguards in the game.

I think I read in some forum that one of them is a fake that you get if you screwed up the main quest or something.

The other is a different one you get if you proceed with the main quest with a different way than the standard one.

Is this true or a bunch of crap. I did indeed check the construction set and there are two more wraithguards but I dont know if they really are what these people say (a fake and a different one).

There is ONE real Wraithguard in the game- the one Vivec gives you and teaches you how to use. If you for some reason decide to kill Vivec, the Dwemer Artifact in his body can be given to Yagrum Bagard, the Corprus-afflicted Dward in the Corprusarium, along with Kagrenac's planbooks and journals, and he will construct a new Wraithguard. This new Wraithguard takes away around 200 HP, and looks like a Daedric Gauntlet when equipped, but otherwise has the same function as the real Wraithguard. The Dwemer Artifact obviously disappears when Bagarn gives you the real Wraithguard.

Yeah, there is a fake one in the CS, and it is mentioned during the main quest I believe, but I don't think it was ever actually put in game. They were probably planning to but as with so many other things during the production process it was dropped.