Generally speaking, the more babies in the litter, the smaller they are at birth, and the slower they grow - that is true regardless of breed. True dwarf babies are marginally smaller than false dwarfs at birth; sometimes they have to do some growing before you can really tell the difference. By the time they are old enough to sell, the longer ears and faces of the false dwarfs are hard to miss.
A young doe usually has kits that are all pretty close to the same size at birth. As she ages, that can change. Also, in a really large litter, embryos that implant close together can interfere with the growth of each other's placenta, restricting the amount of nutrients to each which results in babies that are somewhat smaller at birth.