I'll try and help- Yes, you can wire your fog lights directly to the powered Aux wire in the engine bay (assuming you don't exceed the rated amperage) without having go into the cab at all. Looking at the wiring harness behind the battery, there are two bundles of wires for the Aux circuits. I'll call the powered bundle Group A, and the unpowered/pass-through bundle Group B. I found Group A (powered) on the left-hand side of the wiring harness, while Group B (pass-through) on the right-hand side of the harness. Here's the bitch of it- Ford folded up and wrapped these two Groups onto the main harness with black tape, and they're a PITA to see if you don't know what you're looking for. Nobody likes to start yanking on wires in a $60K+ new vehicle, but trust me, they're there. I recommend you check your manual addendum for the colors of the various Aux switches to help you spot the correct colors and verify you've got the right wires. They will be in groups of six with the ends dipped in an insulating plastic- very distinct. The wires are also different gauge sizes corresponding to the amperage rating, and the 5A Aux wires are really thin (not sure what gauge) which may surprise you.
The Group A/Powered wires are controlled by the interior Aux switches, and you can wire directly to them as they are controlled by a relay and fused from the factory (check the amp ratings again and use the right wire!). The Group B wires are only pass-through wires that go from the engine bay into the passenger footwell. You can use the Group B wires to run power from an Aux switched circuit into the interior for use by something like a dash cam or radar detector. You would do this by connecting the proper Group A wire to the proper Group B wire in the engine bay (splice them together), and then finding the proper Group B wire in the passenger footwell and connecting it to your accessory. FYI- the wires in the footwell as also a major bitch to spot and pull out, just like in the engine bay but worse (at least in my case). As an engineer and former mechanic, it kills me that Ford couldn't make the wires easier to spot and access, and maybe make them 6 inches longer for convenience. Should be easier to use a feature like the Aux switches for the regular joe.
For me, I'll have my driving lights on Aux 1 and Aux 2, and I use Aux 6 for powering my dashcam on and off as needed for privacy. Very happy with the layout. Just take your time.
Hope that helps.
