50Mbit, 28ms latency wireless link at 12km distance, and on a battery budget, eh? I'd love to hear more, I love science fiction.
We were watching a neighbor's house over the holiday, which meant mostly checking for delivery boxes on their porch and putting them inside. We could drive the Mini2 out the window of our house and 2 blocks away to check the porch without getting out of our seats. And this is a suburban area full of houses, trees, and a shit ton of interference at the wifi/4G/LTE ranges. The video never lost a frame.
Random drones floating through neighborhoods is sketchy from a safety standpoint but also it tends to upset people, who often think that any drone they see is spying on them. Just a consideration.
Personally I like to fly around abandoned buildings and decrepit structures. Lots of interesting flying to be done and cool vids to be taken, and there's nobody around to complain :)
I've had my Mini about a year and have yet to have any interaction with strangers who see it flying.
If you tear down the hardware, it's using an Imagination IE1000 802.11ac frontend, Skyworks amps, and a custom DJI image processor chip (marked P1). So the air protocol probably looks somewhat like 802.11ac (OFDM etc.) but without the framing overhead and presumably without TCP/IP.
6 mile range test: https://www.youtube.com/watch?v=4X8ExuJWt6E