An FAA license based on your non-US licence is exactly that - a license. It is the same credit card sized format as a stand-alone FAA license.
On the back, under "Limitations", it says:
Issued on basis of and valid only when accompanied by United Kingdom pilot license Number(s) UKPPxxxxxxxxx.
All limitations and restrictions on the United Kingdom pilot license apply,
Yours would say "German", I presume.
If you have a night validation on your non-US licence then you can fly at night in the US. (As you're probably aware, the stand-alone FAA PPL includes night.)