If you are talking about the one that screws in the side of the tank, it will only let air out "if" the water is below the float.
They do come set at 25psi. That means if the water is below the float, it takes 25psi to push air out the release hole.
Raising or lowering the psi on the air release will not make that much difference in the amount of water in the tank. If the psi is set to high, it will not release any air, and will not work properly. That will cause you to get air in the lines.
The water level in the tank should be around 14 to 16 inches from the top on the tank you are using now.