Hi Andy,
When you have the SimpleBLEPeripheral project open in IAR, you can select the build configuration near the top left of the screen, at the top of the pane called Workspace. There select CC2540 or, as the case may be, CC2541 build settings.
The differences between build configs can mostly be found in ALT+F7 -> C/C++ Compiler -> Preprocessor -> Defined symbols.
Best regards,
Aslak