If I may jump straight to some questions.
I'll try to provide some answers to the best of my knowledge, after a brief scan of the code. There is a chance I may have missed something though.
1) What is the max poly count ?
There does not seem to be a limit other than available memory.
2) How many materials. ?
SAme. Memory seems to be the only limit.
3) What is a standard texture set ?
(albedo, metallic roughness, normal, height)
(diffuse, specular, normal),
Diffuse, specular, normal, parallax, with provisions for additional textures such as emission and illumination maps and possibility of incorporating external textures if needed. Greyscale maps can be part of other textures by embedding them in eventually spare alpha channels.
Are there any "off the shelf" shader workflows that could be preseted in Substance ?
https://www.allegorithmic.com/products/ ... e-designer