Ahhh just saw your edit. I have read about face weighted normals before but have not used them at all. I ended up going the non-square texture route this time but need to look into face weighted normals more as I have heard they can help with gradients and such.
Thanks for the reply. I have used non-square textures once before when i followed the Tim Bergholz Kukri Knife tutorial but didn't understand how it worked on a technical level because it had to be baked at a square resolution and then output out of Substance Painter in 4096x2048. Does Substance Painter double the density…
I don't know but its all is getting pretty clear once you realize that a normal map is just a non100% precise way to compensate the shading gradients vertex normals produce. When you see a subtle vertex normal inclination due to some mesh irregularity there always would be a shading gradient accompanied by normal map…
Just check it with color picker first. It should be "flat" 127 maybe instead of 128. Should be compressed into same 0.5 value for an engine basically. If it's all right and vertex normals are perfectly ok too without giving any gradient then it's nothing you could fix. One trick I used long ago when we had this compression…