I can't help you with logitech, but using my CH software if you set sensitivity below 100% then you lose control movement. So 75% sensitivity would be a loss of 25% control deflection. Looks like that is the Range setting on yours.
I prefer no deadzone at all, or just whatever it takes to compensate for the slop in the controller, which shouldn't be much on a new stick.
I used to run curves in the pitch and yaw axis to make it less sensitive toward the middle, but I took those out as it made it too sensitive near the end of motion, resulting in stalling easily.
Lower control settings may help in the beginning, but will hinder you later. Once you are comfortable with the way the planes handle, then I recommend going back to full control authority.