Same as always. Guys that barely graduated high school arguing thermodynamics.
No, you can’t flow water through the radiator too fast to cool it. An old wives tale for sure, but we’ve beaten that horse to death many times and people will never let go of it.
You can spin a pump too fast, which can cause cavitation and that will hurt the cooling of the whole system. So you have to match the pulley size/engine RPM to what the pump is designed to work at. But too fast through the radiator to transfer heat? No.
And the brass vs copper thing again, oh boy!
Yes, copper has better thermal conductivity than aluminum does. Absolutely true. But you can run larger and thinner tubes in aluminum compared to copper because of the differences in material properties. So can an aluminum radiator cool better than a copper radiator? Yes, it can.
But it depends on the application. If you build two identical radiators based on the copper/brass radiators construction, the copper/brass radiator will cool better. But if you use larger tubes in the aluminum radiator than you can use in the copper/brass radiator, it’s not as clear. You’re not typically comparing apples to apples, a radiator design made to maximize the properties of aluminum is different than the design that would be used for copper/brass. So you have to compare the individual radiators, it’s not as easy as saying copper is better than aluminum.
Here’s some basics of it, of course the info is from Griffen so…
https://www.motortrend.com/how-to/ccrp-0211-aluminum-or-copper-radiator-for-your-car/