Either should work provided you orient the CTs appropriately for phase. I recommend before combining that you plug each CT sans the splitter and insure you are getting positive power.
As far as the capacity issue, the CTs should be fine, even in your worst case scenario. The reason for oversizing is to insure the combined input doesn’t exceed the ADC capacity. The unit is conservatively rated at 50mA. There is about a 15% overcurrent tolerance so the IoTaWatt can actually handle about 57A before it maxes out. Overcurrent beyond that should only result in the an incorrect low reading.
If the condenser starts drawing 30A or even 25, you will probably have bigger problems.