Option one is my suggestion. I believe that in the 2005 Suzuki Cultus the radiator and ac condenser sit side by side with a minor overlap of the condenser over the radiator. This means that when the ac is turned on, the radiator still gets the same temperature ambient air it would get when the ac is off (with exception to the small overlap area). Theoretically you should maintain just about the same temp as without ac. Of course the is the additional load on the engine of turning the compressor to consider but modern engines easily cope with the compressor load.
On the other hand if the condenser had been such that it completely covered the radiator, then we could expect a considerable impact on radiator's ability to keep the engine cool during ac use as the air reaching would be considerably hotter after going through the condenser. Putting a thicker radiator will increase the water volume of the cooling system and will bring down the engine temperature. This is an old school trick. Do not go for a used radiator from the radiator walla.
