To answer your question about water going too fast through a radiator, no you cannot go faster than coolant can reject heat. Coolant rejects water at the same rate of the speed of electricity, so it cannot happen.
One thing that can happen is adding a restrictor, or themostat, will raise the pressure of coolant in the block. This can eliminate steam pockets by increased pressure making the coolant more efficient. I believe this is why the "coolant traveling too fast through the radiator" myth persists. Adding a restrictor removes the steam pockets, giving the coolant more area in the coolant jackets to absorb more engine heat. Raising the pressure in the block does make the coolant more efficient in absorbing heat in areas that would have a gas bubble at lower coolant pressures. Gas doesn't absorb heat nearly as well as liquid.
Keeping the coolant restricted, and raising the pressure internally in the system has the same symtom of slowing flow, but is actually connected to the myth of how fast/slow liquid coolant can absorb/reject heat.
It's important to have good coolant pressure to raise coolant efficiency, so there should be a restrictor, or thermostat in the system to raise pressure to keep steam and gas pockets at a minimum, not to slow coolant so heat has a chance to transfer to the coolant.
Hopefully this dispells some of the myth of coolant traveling "too fast" through the radiator, because if there was any truth to the myth, it wouldn't pickup the heat from the engine to begin with............
It's pretty easy to see how the coolant getting restricted, showing a higher pressure in the block raises efficiency, showing a cooler system is misinterpretted as coolant passing too fast through the radiator to reject heat appears, but it's not a fact that bears out through physics.
Remember, Pontiac engineers actually used smaller pulleys on the A/C, H/D cooling options to speed up the waterpump RPM.
