Hi Buyaka,
We were already aware of the possible confusion related to the DrawDebugCone function taking radians instead of degrees, and we have updated the comment for the function to better reflect that. You should see that in a future version of the Engine.
I am a little bit unsure of the confusion regarding the height of the cone, though. Would you be able to better describe what you are trying to achieve? I created two cones with identical settings, except one has a half-angle of 30 degrees and the other a half-angle of 60 degrees. Then I used both of the function calls you provided to see what the difference would be.
The blue cones use the first function call you provided and the red cones use the second function call. It would appear that if you want to be able to specify a specific height for a cone, you would want to use the first call since both of those cones are the same height even though their angles are different. Am I misunderstanding what the issue is?