Looking at the distribution of light across a given area, one advantage of LED´s, is the ability to spread out the light_source, to multiple sources. When looking at any grow light, the intensity and thereby umol/s/mm2 will be less at the perimeter of the beam. Compared to larger (500 LED´s x 5W) LED grow lights, The GEM will be  considerable smaller, but will have the advantage of a even distribution of photons.  By design, THE GEM can get closer to the canopy. By having the same LED count, that is on multiple GEM´s. The ability to micro manage each channel of LED´s is of course a mayor benefit. Networking each module, you can monitor and control variables like temp, cooling, power consumption and so on. 

Using the USART connector, a Bluetooth Low Energy - Mesh network should be possible.

Another advantage  of spreading out the  LED´s, over a larger area, is the fact that you can cool each module separately and thereby more efficiently.  

The amount of light needed for any given crop is entirely dependent on your ambition regarding growth, power consumption, temperature of lamps, longevity of LED´s as a function of temperature, intensity and time.