Actually, compressor output for our cars varies with both engine speed and evaporator heat intake. We have variable-displacement compressors.

The condenser needn't be in direct contact with the radiator, but you should have some sort of shroud to help the condenser get all the air that it can.

As for the "capacity" of the system, the PFC has a higher capacity to dissipate heat, but probably a lower capacity for holding liquid refrigerant.