I have the 19 and can carry 8 dozen to 1 pound of minnows and can keep them alive for 24 hours with an on board air pump with two hoses for more oxygen saturation. You don't really need two hoses but the bigger cooler you might want to use two or an oxygen system to keep them alive longer.
Engel's are a great bait holder. You could even use the 30 quart as a live well if needed I bet.
USAF Retired and Fishing!