2km is a long way! you just wouldnt be flying that far away unless you are mad with fpv, even then its still a good distance. Its when you start to fly behind buildings and trees that kills 2.4ghz stuff. (lower the frequency better it is through buildings etc...)
I HAVE ONLY EVER BEEN UPTO THE LEGAL LIMIT OF 400 FEET!
(honest guvna)
Difference between the wedge shape receiver and mine is ports to side of receiver to add telemetry add ons.
I wouldnt bother with the telemetry just yet on the frsky stuff, there are better alternatives when you understand more what you want to do with your machine.