So turns out your Razberry is a generation newer than mine. Dimensionally the same except yours has an extra strip of PCB running around the front (end furthest from the GPIO) and right side closest to the USB ports with the antenna embedded in it.
Hight-wise, they are the same, and it clears the edge of the Argon One case with about 2mm to spare, so you shouldn’t need an extension header for the GPIO 
The case add-on is this one: Argon One Active Cooling Addon
It’s working a charm so far