Heres a few things you should should consider when writing vore stories combined with other fetishes (I.E breast expansion, weight gain, etc.).
If your pred is a female and you want her breasts to grow from her prey, it would be very logical for your pred to target girls who are in shape. A skinny girl with big boobs is a lean meat, which means she packs phytoestrogen, a hormone carried in chicken and other leanmeats which help girls develope larger firmer breasts.
An obese or fat girl as a prey mean shes been eating unhealthy, most likely G.M.O, foods, so she carries less phytoestrogen. The unhealthy fats the girl eats settles in her stomach, which means her prey will also gain what most call "unwanted" fat. This fat settles on the stomach and thighs.
For absorbtion, the prey should typically target prey with the body type they wish to take on, as most absorbtion stories have the preds body change from the absorbtion. Like with the last two, a skinnier girl will result in bigger boobs