Use case for triangles or indeed ngons, is when a given surface would generally be flat (planar) particularly applicable for mechanical hard surface objects - shape and their mesh boundary, has either a bevel or chamfer applied before enabling a subdivision/turbosmooth operation because it may not always be an option to…
I would create a mask from ao, curvature and a grunge map an use that as a starting point for roughness. Fiddle with that until you get something with more variation I would also add some blurred noise as a normal - masked by ao - in order to create some dents and wobbling in the surface
Because that'll just create a basic phong material, which is a basic representation of surfaces in real life. There's many view dependent, surface dependent effects that occur on surfaces that simply phong spec diffuse and normal can't express.
yeah looking at the lowpoly, how straight the lines appear. i assume they built the lowpoly first, then used it to create the highpoly, not sure if it was actually sculpted or maybe just smoothed, baked and all surface detail is just done in a software like substance painter.
I would use noise to help distinguish between the different materials and surfaces. As it is now you have it spread across everything pretty evenly. It would be much more readable if you varied the noise/amount from surface to surface. Also, some of your hard surfaces are pretty soft and lumpy. There should be a distinct…