Apologies if I'm wrong here, but I'm assuming you haven't used VR before?
As others have said, it's impossible to really describe / get across to someone until they've experienced it, but honestly, the FOV of the headset is basically how wide your view of the world is. Imagine wearing a set of swimming goggles or a dive mask.
The 'cockpit view' in GT7 is irrelevant once you're in VR, you aren't looking at a view, you are just in the car. I can't articulate it any better than that, there aren't angles to worry about or things limiting what you can see, as far as your brain is concerned and your vision, you're sat in the car, you can see the same way you can see sat in a real car (with the exception as above that it might be a bit like you're wearing a mask that slightly limits your peripheral vision).
It really isn't like a cockpit view that you can move with your head, you genuinely are just in the car, it is the most natural feeling thing and if you haven't experienced VR before, it is going to blow your mind