Ya, as slo-v stated, with the first option, 12 amps per motor = 24 total = 5.25 minutes.

You could theoretically use that 3200mah pack, it is still 3S, so the 11.1 volts stays the same which is the important number. The mah number is just the capacity, runtime basically. However, going from a 2100mah to a 3200mah is a big jump in weight. It will throw off your COG in the plane and the plane will fly heavier and slower.