Thanks a lot for responding Eric. The main style they're going for is, Stylized with realism, hope you understanding what it means, kinda like Pixar animated movies
Metallic and roughness are black and white (o-1) value only like Eric said. This is why they won't accept and RGB value and only a slider in your experience.
Eric, this is version 1 of the nMaker, but I used another process (not very accurate) to generate the maps. Here are the comparative (I had forgot to do) Download nMaker1