On the Ham Standard it doesn't matter much whether the engine is left running or not. In the overspeed case, the prop pitch is out of control, determined only by airspeed - windmilling. Bring the power back, but engine torque only plays a bit part in the equation. A running engine, however, should supply oil pressure, which will be necessary if you have any chance of getting the prop back to feather. Also consider if you have a auxillary prop oil reservoir that is filled by only be an engine driven pump.....without an operating engine you'll need to motor the thing electrically to fill that tank to have oil to play with to advance your feathering agenda. Again, this is very specific to the Ham Standard on the PW118, I'm not sure how the CT7 gets oil to the prop.
Our overspeed checklist called for bringing the power back, getting the airspeed down to as little as 125kts, trying manual feather, electric feather, and then trying to dry motor the engine for the reasons discussed above.