read the thread to get the answers to your first post.
among two wheels with similarly wide tires, the one that is smaller in diameter will have a smaller contact patch. a smaller contact patch generally equals less rolling resistance, all other things being equal. i.e.- no one is using an aggressive mountain bike tire on their road touring bike. I think pan's comment about tire choice is pretty accurate. mtb tires under 1.5" can seem elusive at times. A lot of 26" touring appropriate tires seem to get no narrower than 1.75 or 1.5.