The autofeather system, is monetring the engine torque output, and will if the torque of the engine drops below a level where it contributes to giving power to the aircraft, feather the propeller on the relevant engine. Placing the propeller blades in the postion where they create the lowest drag. So it's not a systems that control the engines in any way, just monitor the torque level on the engines. In case of a engine failure above V1 on a prop aicraft this sytem is redusing the time the failured engines propeller create extra drag, and therefore is a great safety enhachment.