About breastfeeding, is there a difference in the flow rate of breastmilk between small aa breasts and regular b or c breasts? Do aa's flow slower?

Flow rate. There is no defined or discovered flow rate difference based on breast size that i'm aware of.
No! Breast size does not impact milk flow or volume. In the newborn period follow your baby's weight often to be sure adequate milk supply is allowing normal growth. Babies grow 1/2 -1 ounce a day the first few months (after the first week's weight loss!).