On the beech 1900 we used 1700 (full) prop rpms on takeoff, then brought it back to 1550 for climb. In cruise it was 1450. torque was set initially at a minimum of 3,000 ft/lbs on takeoff, it increases as you roll down the runway (not allowed to exceed 3400 ft/lbs). We'd increase power to maintain torque until we got to 750 degrees C on the ITT and then take what we could get in the climb. For cruise we'd run 730 on the ITT.
Prop rpms were to both be easier on the engines and reduce noise (book for the 1900C actually had you keep rpms at 1550 all the time after you pulled it back for climb for best power etc, but down to 1400 was authorized and 1450 was much quieter). This is also fairly true with constant speed props on aircraft engines. You don't want to lower rpms too much because then you're really lugging the engine down. You also get your best POWER out of high rpms. Full rpms will give you most power at any point. You aren't setting a prop pitch, you are setting a governed speed on the engine, which is why the transmission analogy doesn't work. The prop pitch will do what it needs to do to maintain that speed you set. IE, it'll get more bite to lower it or go flatter to raise it. That's the big advantage of constant speed props, you can have a flatter pitch on takeoff to get the engine straight into the power band for thrust, increasing pitch as you move to keep it there (and not overspeed) and then increase it more in cruise. You can also keep a higher manifold pressure at a slightly lower rpms to maintain power output while reducing noise and engine RPMs. Max prop rpms are usually paired to an engine to occur right around the torque peak of the engine (the max power it can supply you), but that's not neccessarily the best rpm to run an engine at for longevity or fuel economy. However, high manifold pressure and too low rpms can also be detrimental.
