You are very likely using Optimus as pointed out by circleface. Especially as you mentionned using an Intel driver, I'm pretty sure you are on an Optimus laptop (like they almost all are since the past 3-4 years). Read this: Optimus and this Bumblebee. You need a special configuration to have it work, involving optirun and prismrun.
You probably don't really need nvidia-xconfig especially if using Bumblebee. I think it does that by itself when it starts so you don't need to configure the hidden xorg server.
]]>warning: unable to open/locate x configuration file.
Xorg-server was not found in the pkg config search path.
Perhaps you should add the directory containing "xorg-server.PC" to the pkg_config env variable.
Error unable to write to directory '/etc/x11'.
Yet I've installed nvidia and its dependencies along with xorg and the dependencies the wiki recommends, and I got the error in your 2nd link. And my bios doesn't have a display section or any sort of options that part of the wiki recommends.
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