Annika1980 wrote:

To test it out, I took some photos of the sky at ISO's ranging
from 100 to 3200.

I can make a trivial de-noiser which will produce zero noise under your
test conditions: simply replace all pixels with the average value.

A better test would be to synthesize an image and then degrade it to
various degrees -- add in some white noise -- and then give it to "NI"
and compare the result to the original. One can then quantify not only
the noise reduction, but also the (necessary) detail reduction as well.