For the Service Rifle, your choices are 1/2 MOA clicks or 1/4 MOA clicks. The sights have to look like the standard issue sights and thus fit in the carry handle the same way.
You can also select the aperture size that you think is best for you.
The german contraptions that you are talking about are NOT NM sights, those are for match rifles (or mortars.)
My service rifle has NM sights from ArmaLite.