I don't know that a sock would have to be so large as to prevent touching it. I assume the concern about touching is condensation? A good breathable fabric should minimize condensation. After all, the inside of a bivy is touched throughout the night.
I do like a large tarp, and with today's lightweight materials I can't see a good reason to not go with a large one. I've yet to have problems with rain blowing beneath my Speer Winter Tarp. I have experienced wind blowing beneath it causing a bit of a chill, but if it had been uncomfortable enough I could have easily lowered the windward side. A big tarp can interfere with the view, but, as you say, that can be overcome with some thought and simple tools.