The ram situation was odd from the start. Usually when removing 1 stick and problems go away, it's a decent indication of 1 of 2 things. Either the socket is bad, or the removed stick is bad. Then you changed mobo's. So my only guess would be to try each stick individually in A2 and run the memtest on each. If you get the same results from both, then either both are bad or both are good, depending on the results. Likelihood of both failing is pretty small, which could point to a bad cpu, or maybe there's not enough voltage on the system agent/memory controller. Maybe try manually changing the Cas to 16.
Or maybe even the psu isn't putting out enough stable voltages when the cpu goes into lower power modes.
Are you running Ryzen Master? Maybe try going back in bios revisions to the last revision before 3rd gen cpus were included, I've heard rumors that there was some stuff dumped to make room for 3rd gen stuff/fixes.
Windows on Balanced power mode?
Wall of text again, so I apologize in advance.
I guess I'll dial it back a bit further to my previous issues; while I'm still waiting to see if this random stop happens again, it can never hurt to give more information.
I bought my parts around June of this Summer, and everything seemed to work fine up until the Fall Windows Creators Update, at which point it began to throw often, and seemingly random BlueScreens. I don't know if it was SPECIFICALLY caused by a Windows update, but it only occurred after this update. The BlueScreens it threw almost always threw blame at ntsokrnl (the system kernel) or nvlddmkm (NVIDIA driver files), which apparently isn't too uncommon for 1060 owners, but uncommon enough that there doesn't seem to be a clear answer. However, because the errors it threw commonly had to do with memory, I decided to run MemTest86. It errrored out hard on Test 1 only, and only when both sticks were in. Otherwise, after around 4 passes on each stick, in each slot, it seemed like each stick tested fine individually (which didn't end up giving me errors until the first crash I talked about before installing my board).
However, after settling on the one-stick solution, I decided to go back and see which drivers were updated when the Creators Update came around, and the only significant one that came up was the AMD RYZEN chipset. This is why I'm so speculative on if the chipset, specifically the PCI/E one, could have caused these issues, potentially causing the Graphics Card to miscommunicate with the RAM. I decided to not jeopardize it and leave it with the single stick as long as it ran stabilly.
However, the two that concern me the most are the MemTest crash and the crash out of BlueScreen. If Windows wasn't actually running when these two hit the fan, it worries me that the issues may be on a hardware level as opposed to a software level, but as you can tell, I'm not the most educated on issues like this.