Hi,
The Narrow bore in D is only mellow in sound and the Pitch D in wide bore is louder is that right??
John
The idea behind developing a narrow bore D (narrower compared to the Rowsome style wide) involved a bit more than just volume. A wellmade narrowbore/small holed design has far reaching implications for tonal quality and colouring.
I agree, the Narrow-bore Angus I played wasn’t just a quieter version of a Regular D. It had a wonderful sweetness and tonal complexity that was very different…nice.
But, if your question is whether it plays the same scale and is essentially the same instrument as a standard bore D the answer is yes. There is no difference in the fingeringin or anything just the sound. 
Doc