What a DJI is capable of rangewise and what you can /should do with it, are very different things
standard transmitters on the DJI can be swapped out for more powerful modules and you can get about 5KM out of them (NOT approved)
Friend of mine has stood on the northeast coast and flown his out over holy island and back. (Not legal)
Don't know about other countries but in the UK you are not supposed to fly further than line of sight which is considered to be 500M horizontally or 400M vertically. (even if you have a live video feed from it) Unless you have CAA permission. this can be even less if you are near restricted airspace.
there are a lot of other restrictions, governing flight over public assemblies, flight near buildings or structures or vessels etc
Rangewise the DJIs are clever enough that if they exceed transmission range they will either retrace their steps until they re-acquire or they will fly back to pre arraged GPS co-ordinats, usually their takeoff position
G