yes, you can lock the framerate to the monitors default refresh rate, but this doesnt guarantee that X-Plane will maintain that rate. Should your cpu or gpu not be able to cope with the demands being placed on it, x-plane will 1. throttle your frame rate, 2. request that you increase the number of frames drawn and 3. introduce a fog as needed to blur out distant objects and allow an improvement of frame rates.
The easiest way to view the above settings panel is realizing that the settings at the top left, are all cpu specific, and at the top right gpu specific. This allows you to easily tune your machine to eliminate any bottleneck that could be slowing you down.