Starting in Maya, Sefki shares his techniques to light the character model, utilizing area lights, HDRI maps, and light blockers to establish the right mood before adjusting the camera to achieve the very best likeness of his digi-double. This comprehensive workshop by Sefki Ibrahim demonstrates how he approaches the look development of a digital double, and covers his complete process for lighting, shading, and rendering using Maya and Arnold. Until Arnold updates their shader to work correctly with tangent space normal maps and hard edges that's really all you can do, it's very frustrating.Whether it’s in movies, TV shows, music videos, or video games, digital humans are everywhere. To fix gradations add extra edge loops or bevels to the low poly. Triangulate low poly mesh, soften all edges, bake in Painter, preview in Arnold render with exact same triangulated mesh and ignore what you see in Painter. Ironically how you fix gradations is by hardening the low poly normals and re-baking, so you really only have one option here which is not a good one. The reason you don't see gradations in Painter is because they use Mikk tangents and their viewport shader is better than the Arnold aiStandard shader.

Having any hard edges creates seams in the final render, but softening all the edges creates gradations like you have in your render. Now for the bad news, as far as I can tell Arnold can't correctly render a tangent space normal map in Maya unless you soften all normals. In Maya you must use that exact same mesh, the triangulated one to apply the normal map to so the triangle direction doesn't flip. In substance make sure your mesh is triangulated before you bake the normal map. The issue you're facing is because Substance Painter uses the Mikk tangent space and Maya viewport and Arnold use something else.

Substance painter to maya arnold