[briHass]

There's also significant engineering calculations and guidelines/rules about the expected volume of air that is expected to enter/exit vents vs their size and grille restrictions. This is more to prevent loud airflow, but there's also charts for air distribution for room sizes.

Now, most HVAC contractors go by gut feel/rules of thumb, but if you want to pay for it, a well designed system would never be 'windy' or noisy.