Now you know throttle 1 controls the engine power, you may be interested to know the RPM affects the prop pitch, so in low RPM the pitch is course.
If you ever glide with auto climb speed turned on, your aircraft will glide at what is your normal climb speed. While it glides, play with the RPM as you will find you can glide a lot further by settting RPM to the minimum. In normal powered flight you have the prop set to maximum RPM and leave it there.
As FLS has indicated adjusting RPM and throttle can conserve fuel, but I think in general play very few use it unless escorting buff a long distance.