Just for information, Antenna Gain applies equally to the Antenna’s receive and transmit performance. The gain or extra power has come from moving some energy from one direction to another. Normally this comes from flattening the radiation pattern and reducing the power that radiates at an angle both up and down and moving this to the horizontal direction. In this case the antenna still radiates equally in all horizontal directions, just less towards the sky and less directly underneath the antenna.
A “directional” antenna will also concentrate the power in one direction. No longer does the antenna transmit or receive equally in all horizontal directions.
The key take-away is Antenna Gain is the same in both transmit and receive. A Higher Gain antenna will improve receiver performance as well as increase apparent transmit power toward the horizon.
Typically nodes transmit with less power than a Gateway so the weak link is the Uplink direction and a Gain Antenna can assist a Gateway receive a weak signal. In this case turning down the Gateway transmit power to the legal limit should not reduce the system’s performance.