Just my opinion, blues then channels then flatheads. Best size for fillets is between 4 and 8 lbs. Fiddlers, 1-2lbers are best for whole cooking. Anything over 10 is too big but can be cut down to be tasty. I have used deer liver and works pretty good but my best bait hands down is cut skipjack herring. Liver generally works best on smaller fish and typically channels. Whole live bluegill are best for flatheads, bigger the bait bigger the fish. Blues typically hit cut/bait-fish best.