It's the number of parallel threads executing during the speed test. It roughly corresponds to simultaneous users creating traffic during normal use.

The Outdoor Wireless Link Calculator from Ubiquiti may be helpful to calculate the fresnel zone and required height of the best mount position of a CPE: https://airlink.ubnt.com/ As for antenna angle...

Gary H wrote What mode would I configure the hardware for the link from Location 1 to 2 and location 2 to 3 ? All in Bridge or some other configuration ? I would not use bridging mode except you...

Same is true for the EAP Controller. I would like to manage EAPs and CPEs from our Linux-based hotspot gateways. A first step into this direction would be the release of the API by TP-Link.

"Standalone mode" means you use it stand-alone, without the EAP controller software running on some PC. Emulator is here: http://static.tp-link.com/resources/simulator/EAP120_1.0/index.html

If your camera, the EAP and your wireless clients all use static IPs, this would work with the EAP in standalone mode. If you need to use dynamic IPs (DHCP) you will need a DHCP server somewhere...