Here's the simple science: more air means more dilution. When you open up the airflow, you're mixing more oxygen with the vapor, which makes the flavor lighter and the vapor cooler. Close it down, and the vapor becomes more concentrated, so you taste more of your e-liquid.

If you're after intense flavor, a tighter draw is usually the way to go. You'll get a stronger hit of your flavor profile, whether it's fruity, dessert, or tobacco. On the flip side, an open draw might mute the flavor a bit, but it gives you a smoother, less harsh throat hit.