Can't launch on device iOS

To build a release editor, press the Cmd key, Shift key, and < key simultaneously. That will bring up the scheme editor for the currently selected scheme (make sure UE4Editor is the selected scheme). In the Info tab, you can change the Build Configuration from Debug to Release.

For your other, since it looks like you are building from source, you will need to build the UE4Game for IOS. To do that, in the same project that you use to build the editor, you will find a scheme called UE4Game. Select that scheme and select IOS as the target platform (right next to the scheme selector) and then build that. You will then have a UE4Game-IOS-Debug and if you do the same thing you did for the UE4Editor scheme (above), but for UE4Game, you can build the release version it is looking for.

-Pete