I am wondering what is the sense of having RPM's in sport mode ? how do I change that to speed reading or the radar reading  , I do not care about the motor RPM's I would like to see either KM/h or M/h, can that part of the app be personalized , is there actual speed reading in the DJIgo ? I am curious to see how fast my P4 moves at times...

I think the RPM is just for show, but you should see an indication of Horizontal speed, and you can chose to display mph or km/h.

As Aardvark points out, the speed is displayed on the DJI G0 screen.  (Along with the altitude and distance).

The RPM indicator has worked for me..   In Sport mode, on occasion I've had it turn red and give me a warning about 'Rpm too high'.  (I like to fly fast )