@SteveMcniven 

Hi,

The "Wi-Fi Coverage" setting adjusts the power of the wireless signal(s).

You can compare that to the "volume" adjustment of a loudspeaker. The higher you turn up the volume, the louder the sound becomes and thus the farther away from the loudspeaker the sound can still be heared clearly.

As for selecting the optimal setting you can only test this by yourself. If you can still get smooth video feeds from your cameras at the "intermediate" or even "minimum" setting, then there is no need to have it at "maximum".

  @woozle so minimum would be optimal if I can get away with it as there will be less noise... yes? It's not in itself slower, just less range

  @SteveMcniven 

The maximum achievable data throughput will decrease with less power. But not all use cases require maximum data throughput.

For example, let's say the range extender could achieve 50 Mbps at the "maximum coverage" setting and 25 Mbps at the "minimum coverage" setting at the location of the camera, but your camera only needs 5 Mbps for its video feed. In this case it wouldn't matter.