I see. I just looked up both of those upscaling techniques, and it might be easier to vary which is used on which type. For example, ESERGAN was trained to use Manga images (Which probably explains the oil painting results)
Metal is notoriously difficult if the basic texture doesn't have enough detail, since the algorithms tend to soften out contrast and metal requires high contrast to look right.
For that example you showed on the second to last photo, the contrast and detail could be remade in Photoshop with a combination of layer effects and gray overlays for the metal edges.
However, I understand that this would interfere with how quickly you accomplish these, so hopefully there's just an AI algorithm out there that can handle metal rather than adjusting them by hand. If not, at the very least your work on smaller things like switches and more natural decorations like the Kashyyk greenery will be able to be upscaled.
Otherwise, one technique that I've learned which works pretty well for metal is in Photoshop. Filter - Diffuse (Set to Anisotropic)
This is a result from the Player Armor in Kotor 2.