1. Why not simply use the 4 pin ATX connector coming off the PDCB? Is there any benefit in directly wiring to the AC-DC switching?
This is because a cheaper PDCB cannot handle the full current of a GPU + CPU. I am currently using a $12 aliexpress one with my 1060 and G4560. You certainly shouldn't go that cheap, as the $18 pico-box one is a better choice.
2. Why pay $70-80 for PDCB, Meanwell switching, and soldering/PSU shroud if the case is already large enough for an SFX PSU?
I'm just merely pointing out the lack of any mainstream cases taking advantage of such a small form factor. Any case that can support a FLEX ATX PSU has enough space for a meanwell EPP-200.
Secondly, we are on the bleeding edge and very niche builds. The biggest reason why I went with a 12V build is the low number of wires you deal with. Building in such small spaces, when you only have to hook up 6 wires is an amazing feeling.
And finally, you'll never approach the cost effectiveness of mass-produced and mass-distributed PSUs. That's the price to pay until SFF becomes mainstream.
3. I am considering the L4, but it's a bit expensive (over $100 USD). Might be willing to splurge if not much modification is required. I'm not sure how I feel about paying a large premium for less space. We'll see.
Lone Industries has an EPP-200 in his hands
. I think he will try to support it. It is a lil' pricey, but it's low runs, and is powder coated. You have to pay to get the nice things in life!