I think it would be best to stick with the auto brakes RTO. They will maximize braking effectiveness to release just enough which the pilot would likely not be able to do.
If I remember correctly, some or maybe all Boeings inhibit anti-skid at 15 knots. If that happens on auto brakes RTO, that could create a skid at low speed. But I think going to manual braking near the end of the runway would result in a similar outcome.