AGBagb - Activation of the both stab cutout switches should disable all electric control of the stabilizer. One can, however, imagine a failure that involves one or more electrical shorts that yields runaway stabilizer that is not arrested via the cutout switches. For that reason, the checklist has #4 suggesting that as a last effort, physically stopping the trim wheel on the flight deck will freeze the stabilizer. MCAS should be disabled via activation of the cutout switches. Short of a failure with the stabilizer electric motors that is separate from MCAS, activating both cutout switches will stop MCAS from moving the stabilizer.