With RE700 and ITELITE flying with original DJI VISION app I get around 2000-2500 meters.(6500ft - 8200ft) (didn't test exactly it depends on the zone I fly in if I fly over other wifi networks etc).
A good example would be almost 2000 meters over houses filled with WiFi hotspots and networks and small buildings (that I did 1 or 2 weeks ago).
My main problem is that I lose RC signal ! (I have it set to FCC) so I can't test my max FPV range since the bird autoflies back because of RTH kicking when loosing RC signal.
I have some documented flights but I remember that in all of them I lose RC signal at above 2000 meters. (6500ft) sometimes it goes further sometimes not.
For me anything above 1000 meters is more than enough since I only fly to capture some nice videos
so I'm happy ! Not sure if I will buy an amp for the RC signal ... in worse conditions I get above 1000-1500 meters (~3500-5000ft) so its quite good for me. (I haven't flown over a city or bigger buildings, only above houses and smaller buildings that have their wifi signals).
Couldn't find a completly free Wifi zone close to where I live !!! I went maybe 20-30 km away to test but I can still find 2-3 wifi signals there. (its actually funny)