Good work, VonMacher.
That sticker on the smaller transmitter looked vaguely familiar. It starts out ... MAC 60601F... and so I did a quick search and found those numbers coincide with the old MAC addresses we used to need to bind a new camera to the 2.4 transmitter and flight app and make it work on the Phantom 2 Visions.
Here is a random thread I found in a quick search:
Tutorial: How to get the MAC address of a new camera
https://phantompilots.com/attachments/p2v-ch-11-png.7471/
On the Vision though, the MAC address was associated with the transmitter in the camera on the AC (If you bought a new or used camera, it would include a MAC address which you would type into your app during the binding process). In this case, it seems to be associated with the transmitter in the controller. So this makes sense if the MAC address is needed to handshake between one end of the wifi connection and the other end. In other words, this seems to strengthen the lightbridge theory because it appears the wifi starts and ends with the controller and flight app. Furthermore, the two patch antennas must be the two lightbridge antennas in the classic lightbridge systems - one for receiving and one for transmitting.
This also explains why DJI uses two different colored cables (one grey, one black) coming from the lower transmitter.
Well, according to tests I made, both side panel antennas are used for exactly the same purpose. If I remove one of those, just slight signal degradation but video and control are still usable. If I remove both, and little stick antenna is connected, I loose drone connection, but WiFi connection to phone is still at -30 dBm, which is more that good.
So yes, side panel antennas are for RC - drone link, they work together in both directions. Why 2? Maybe for wider angle of radiation with same gain.