Having never flown a multi-engined RC plane, I really can't say how much prop torque two generate. But, counter rotating props will nullify that torque, which is really nice. No slamming rudder on take off.
Counter Rotating props are more needed for multi Rotors (quads and larger) to help keep them from spinning out of control since they have no rudder. And their "Yaw" rotation is usually acheived by slowing down a set of those props moving in one direction. Some do have pivit mounts for getting fast yaw rate, or in the case of Tri-Copters, simply keeping them stable.
Most planes do experiance some torque roll. I know most of my pushers get a very bad torque roll at launch, but once enough speed has built up and the control surfaces win the fight its not so big of a deal.