For a product we wear routinely and soooo close to our eyes, it makes a lot of sense to know what's inside the tube!
Basically when you break it down mascaras have five main ingredients:
The varying percentages of each ingredient make it a waterproof formulation, volumizing formulation, lengthening formulation, etc.
The other thing that contributes to these properties would be how dense the bristles on the applicator brush are. The more densely packed the bristles the more likely it is a volumizing product.
In terms of whether or not this contributes to the clumping still boils down to product exposure to air resulting in drying out prematurely resulting in clumping.
The more dense the bristles then more product can technically accumulate. However, if the product is well maintained this shouldn’t be an issue!