The main thing about rads is that some are optimised for high-speed fans, and others low. The radiators that are optimised for high-speed fans have more dense fins on them to help dissipate heat, but optimally need more air to push through them. A rad designed for low-speed fans have a lower fin per inch count and require less air to pass over them to dissipate heat, however they won't benefit as much as the denser rads will from a high speed fan. To surmise:
Low density rad + low speed fan: quiet and moderate to good cooling.
Low density rad + high speed fan: noisy and good cooling.
High density rad + low speed fan: quiet and moderate cooling.
High density rad + high speed fan: noisy and good to excellent cooling.
Thin rad + low speed fan: quiet and moderate cooling.
Thin rad + high speed fan: noisy and moderate to good cooling.
Thick rad + low speed fan: quiet and moderate to good cooling.
Thick rad + high speed fan: noisy and good to excellent cooling.
120 / 140mm rad: stock-clocked CPU.
240 / 280mm rad: overclocked CPU and a single low-TDP stock-clocked GPU.
120 / 140mm + 240 / 280mm rad: overclocked CPU and a single high-TDP stock-clocked GPU. Overclock the GPU if 140 + 280mm rads.
240 / 280mm rad + 240 / 280mm rad: overclocked CPU and dual low-TDP overclocked GPUs.
360 / 420 mm rad: overclocked CPU and a single high-TDP stock-clocked GPU. Overclock the GPU if 420mm rad.
120 / 140mm + 360 / 420mm rad: overclocked CPU and single overclocked high-TDP GPU or dual low-TDP stock-clocked GPUs. Overclock the GPUs if 140 + 420mm rads.
240 / 280mm rad + 360 / 420mm rad: overclocked CPU and dual high-TDP stock-clocked GPUs or dual low-TDP overclocked GPUs. Triple low-TDP GPUs if 280 + 420mm rads.
360 / 420mm rad + 360 / 420mm rad: overclocked CPU and dual overclocked high-TDP GPUs. Triple high-TDP GPUs if 420 + 420mm rads.