To your questions -
1. PSoC 6 supports only one SAR ADC in hardware because it only has one SAR block in hardware (the ADC is not made up multiple Analog blocks like PSoC 1 devices). Regarding resource explorer - PSoC Creator does support one. Go to "View -> Resource Meter" to see the resource usage.
2. PSoC 6 has two Op-amps that can be used to implement 2 S/H circuits with external caps. For 4, you will need 2 additional op-amps externally.
Let me know if this helps.
Meenakshi Sundaram R