Please notice we have a one topic for one issue rule. Your issue was that the Witcher 3 selected the wrong gpu on your hybrid graphics setup. If i understand you correctly this is now solved? If so mark the post that helped you the most as solution. If there is another issue (like how to optimize settings for witcher 3) please create another support topic for it. I’ll change the title of this topic slightly to make it clearer.
Btw, the reason why Witcher 3 remaster selects the iGPU is that it runs on VKD3D-Proton and not on DXVK as the other games you mentioned. The command instructs VKD3D to use the Nvidia gpu.