Or do you always mix this https://cgcookie.com/lesson/building-a-pbr-shader?wtime=252 setup with other shaders to make it PBR (for non-metals)? I mean copying all these nodes, aside of the Diffuse BSDF.
And if so, should you plug the mixRGB to all Fresnel nodes/Layer Weight node aswell?
I don't think all of the materials in Shader Forge are strictly PBR.
Nowadays for most basic materials I just use the Principled BSDF since it does that work for me, but if I need to customize something more than it allows then I will generally use Fresnel and the mixRGB trick is still a good one and you can plug it into all Fresnel / Layer Weight nodes.