Now that both M12 mounts, 2nd WiFi adapter and RPiA+ case have arrived, I have completed more testing. The mounts do not fit perfectly, so I cannot use the provided screws. A little wire works well to hold them in place, until I find a better solution.
RPi2 as WiFi Access Point (bypass my work WiFi, which is terrible)
RPiA+ and laptop connecting to private WiFi network
Stream video using Gstreamer (UDP) and Netcat to laptop.
There appears to be a bottleneck somewhere in the WiFi bandwidth. At low resolutions, e.g. 800x600 or less, the RPis can both stream to the laptop with minimal latency. Anything higher and one or both streams start lagging intensely and data is no longer delivered consistently. The RPi2 is also not receiving enough power at higher resolutions and the power is light blinking. I need to use a better USB cable, as my current one can't carry the full 2.1A of the wall charger.Going to switch my laptop to be the Access Point, hopefully it can handle the bandwidth better if I can get it working. Troubling, as it does not have an ethernet cable to keep internet working.
Note on lenses:
M12 lens ratings (FOV etc) do not translate correctly when used with the PiCamera. Probably due to the sensor size. Either that, or the lenses are not as labeled.