Now I know what you meant by artifacts. The seams being visible.
I don't have the files anymore, so I can't test it and am not in the mood for that.
However, if you look at my first render result after just plugging in the maps except for IOR (metallic parts were absolutely black), the seam at the edges was only partially visible and in some areas merged so that it looked normal.
The only thing that I changed was the Dilation/padding.
Standard is 16px (@2048²) . I didn't change it because I didn't know if there would be a problem and set the padding from +infinite to +diffusion.
I'd say play around with the settings and you should come to your desired output incrementally closer.
BTW, I never said that you should use unreal or the unity shader, it was just to show you that even inside of SP, the look can vary dramatically. Not just colors but also the way metal is rendered.