Quite a bit has happened since the last post. The system is fully assembled without a case now. There is much tuning to be done to rein in the power consumption and heat output under load. Under Arch Linux, I saw the full system load hit as high as 255W (incl. ~20W for the PSU) when compiling a Linux kernel with the CPU set to boost to 3700MHz on all cores and SMT turned on. When gaming in Strike Suit Zero on 1920 x 1080 on High, the system would hit ~170W (incl. ~20W). This is actually surprising given how much power the system could pull in total.
That said, I wanted to play Warframe and tune to system completely so I installed Windows 10, drivers, HWMonitor, Ryzen Master, MSI Afterburner, Ryzen DRAM Calculator, Thaiphoon Burner, and Steam, and started testing. For the CPU, I have been able to achieve a 0.1125V (112.5mV) undervolt. I will work on getting the RAM tuned correctly. I had been able to run the kit using the D.O.C.P option in the UEFI but now that is no longer the case. I have gotten the safe and fast timings and voltages for them using Thaiphoon Burner and Ryzen DRAM calculator. As the kit can go to 1.4V max, I do have some headroom. Now if only, I can figure out a way of removing the red decorations from the kit without voiding my warranty.
Any regrets? Yes. I overestimated just how much performance I needed for the tasks at I'm doing or the games that I play. That said, it is a ~$150-$200 difference and I would hit the ceiling for a lower power configuration rather quickly once I get to compiling and rendering. The extra money "saved" would have gone to cooling, power, game controllers, and saving to the eventual case. The largest benefit of going lower power would have been getting the system to hit a ~200W maximum for full system power usage (with a Ryzen 5 2600) and not needing PCI-E power from the PSU (in the case of the bus-powered(!) RX 560 Aero ITX at 60W(!)). The others would be powering the system from one Mean Well EPP-200-12 + a PDCB and having better overall portability. Speaking of PDCBs, I received a 250W, 12 Volt unit that I ordered a couple weeks ago from a seller on AliExpress and it will not work in its stock form with Full Circle due to its connectors getting in the way. Oh well, time to get the L9a-AM4 for the system now.
@Legion
I did test the T318 on the system before mounting the stock cooler. It just fit and mounting would have been relatively easy if I had the right hardware at the time. That said, my setup would have been such that my results would have ended up similar to
@SaperPL 's.