I have always believed the pellets vs clumps are simply a difference in diet.
Clumps are from deer eating vegatation, grasses etc. Pellets are from deer eating acorns, twigs, and other mast.

The sex of the animal may be (is) difficult to prove from their droppings.
Small droppings = small deer and larger droppings = larger deer.
I think the location of where the droppings are found may be more important than the actual size.