Sure, higher pitch has higher drag, hence load, hence torque at equal speed, but....

Power increases with rpm until you hit the power peak.... which mecam is probably not operating beyond.... let's assume.

If you lower the speed you lower torque (and power). No need to think about the prop so far...

With less pitch the engine will run faster... hence more power hence more torque.

So there is room for confusion here.... is the assumption that the rpm will be constant?