I buyed a vr asset (VR HOME CINEMA) from the asset store in wich there are two camera (one left and one right), and two version of each game objet (for the left and right eye).
But in the official VR Sample Project from Unity there is only one camera, and one version for each object.
Are there two different way to develop a vr app, or I miss somethings?
Yes, The easiest way is arrange two cameras for VR App: one for left and one for right. You can do with one camera but you would have to render on one main camera for both eyes. That will be a bit more difficult than arrange 2 cameras.