NIK Collection 4 as Photolab Plug in - Settings - ICC Profil „as shot“ = Adobe RGB?)

Yes, when you load a Prophoto TIFF in Photolab you transfer „as shoot“ a Prophoto TIFF to NIK. I tried it. The Input Colorspace is always your workspace in Photolab for TIFF Files.

When you use Photolab as RAW Converter, you get an Adobe TIFF „as shoot“ for the transfer to NIK. AdobeRGB is the workspace of the DXO RAW Converter.

@wolf explained it here: