GetControlconfigData primary goal is to have a string representation of configured controls that can be used, for example, to save the configuration on disk (see Input System3.cap). Then you use SetControlConfigData to set controls.
I didn't think of using this method to transfer controls data between two layouts, because I thought you'd rather have one InputSytem global to the application than one InputSystem for each Layout. So, it may and should work. If you try it, tell me if it's really working