In my experience, the perfect scope height is a very personal fit, kind of like boots. What works best for me might not for you.
That said I still think most folks buy too big an ocular bell and mount their scopes too high. I prefer mine at about medium ring height, but for many folks, even medium is too high off the action. I had one 50mm scope mounted in a set of high rings and I did not find it too difficult to align to, but it was not as natural as the medium height for me.
I'd never mount a scope touching the barrel. In fact, I prefer at least .040" clearance to keep the barrel oscillations from harming the scope.