So when I torque all 20 of my car's lug bolts to 120 n-M, I've exerted 2/3 of a W-h? So if it takes me 4 minutes, I'm averaging 10 watts? That's neat. I wonder what the peak wattage (right as the torque wrench clicks) would be; it must depend on angular velocity.

Newton meter as a unit of energy is not the same as the newton meter unit of force for torque.

The energy unit meter is distance moved, while the force unit meter is the length of the moment arm.

This is confusing even though valid, so the energy unit version is rarely used.

You can exert newton meters of force while using no energy, say by standing on a lug nut wrench allowing gravity to exert the force indefinitely unless the nut breaks loose.