The DJI Go App has two types of RTH, Return to the take off point and Return to the controller.

How from the main screen do you tell which is active?

The Mavic will always return to the last marked home point. While you can set the home point to the mobile device's current location, the Mavic doesn't actually return to the mobile device's current location if you move away from the last marked home point.

That I understand, but sometimes the drone seem to return to where I was stood when it launched rather than the launch point of the drone, even though I was pretty sure I set the return as the drones location.

So I was wondering is there an icon on the screen which says what type was last set.

The "H" icon on the map in DJI GO shows the current location of the home point.

Dude, the app will always set the AC location as the home point. But I alwasy set my home point manually and double check it on the map even when the app set it automatically. So there is no guessing