You don't get it, the die area under the metal hbeatsink of he CPU is tiny, more cooling power won't fix the transfer between the tiny area and the cooler, undervolting will, you just need to meet the requirements of the power output, so for example 125 watts. On average the CPU will drop temp but under heavy load, barely any difference because the heat is still transferring between a layer before it gets cooled by the cooler. Both AIO and Air are subject to ambient temps too
I use a Thermalrite Peerless Assassin SE on quiet mode. I had a EK BASIC 360 on it with no difference in temps.
Want pics?