Perhaps you did not understand me or my explanation was poor. If your blower in your first picture was running full speed and you put your hand over the intake hole, no air comes out the output hole. If you barely moved your fingers apart, covering the air intake, a controlled amount goes out the output hole. The motor always runs full speed. I would suppose most electric motors, that have openings and are not fully enclosed, have an internal fan for cooling. They cool better at full speed. Ever block a shop vac hose with something? The motor speeds up because it is under less load. When the hose opening is unblocked, the motor slows down because it is under full load. Ever get a drill motor very hot from turning slow speed with an extra high load, the fan wasn’t turning fast enough to get rid of the heat. That looks like a very nice blower unit. In my opinion, controlling the intake is the best way to control the output. My 2 cents worth, your mileage may vary.