A high-power wireless module can help a UAV sustain a usable FPV video link when distance, platform movement, and local RF noise make ordinary Wi-Fi hardware unreliable. But transmit power alone does not create a dependable downlink.
A high-power wireless module is often considered when an ordinary radio link loses stability before the device reaches its required operating distance. Output power ratings such as 27dBm, 29dBm, and 30dBm can sound like small numerical differences, but they materially affect the RF link budget.