the size doesnt matter for aerodynamics, generally, but it matters for physics.

Drag is a square or cube scaling, i forget which, so at higher speeds it increases disproportionately.

A larger object has more air to move out of the way, which means more drag. It’s more capable of moving that air with it’s increased volume. But then you also start running into volume to surface area scaling issues. Elephants are really slow for a reason, and it’s the same reason small animals are comparatively fast.