I have far more experience with the DX style than the SS style, but my take is that they both should be held at about the same angle. Both held nearly flat as possible while still being able to cut close. Letting the bump of the SS push down the skin behind the leading edge to assist with skin stretching, not to necessarily change the shave angle. But there is more difference when shaving areas like the cheeks versus the jawline with less soft tissue underneath, so it is not exactly the same.
But more important than some specific angle is a light touch.