You could also handle the 12V wiring behind the WFCO "power center" by purchasing this device,
https://www.ebay.com/itm/122894438164. It provides 4 fused ports for "maxi" fuses with 8-AWG wire, and 3 larger ports (without fuses) on the main bus bar. Maxi fuses come in a wide range of sizes, from only 5A to more than 100A each.
These ports accept stripped wire ends without lugs, so you might be able to avoid lugs and the hammer crimp tool to attach these medium-sized wires in the area behind the WFCO unit. (You will still need lugs at the battery end of the main wire., and it will probably need a separate fuse as well).
The nominal wire sizes are around 8-AWG on the fused ports. Smaller wire ends from the the PD Converter output "+12v", and maybe two wires into the WFCO fuse board (if you leave them fused for only 30A with AWG-10 wire), all need to be "built up" in diameter by adding a glob of solder, maybe with a copper sleeve as well.
If you upgrade the wires to the WFCO fuse board to 8-AWG, then you don't need to build up those ends into this 4-way "maxi" fuse holder -- but bending those larger wires into the WFCO fuse board ports is somewhat challenging, especially for the upper left "12V" port. (The diameter is fine for AWG-8, the problem is the lock of room for bending the wires into the ports).
A "battery wire" upgrade AWG-4 (rather than AWG-6) fits the small port of the main bus perfectly, as long as you leave the provided "sleeve" in place. But I would still melt some solder into the stranded bare end, so that the screw-down port holds it better.
That battery wire should have a properly sized external fuse, at some additional cost. For my main "battery +" wire into the WFCO area (it's a long one), I use a cheap ANL fuse holder of the type Wavery showed in his post.