look into, i think Delta's, laptop/desktop external PSUs, they hit the 87-90% but they are a higher voltage DC.
There is also nothing wrong with using a PCIe power adaptor off a desktop internal PSU
Perhaps domestic drivers for LEDs would be a good choice - if they produce 12V and don't try to drive a constant current.
Will do the study. Very interesting.
12V is also not a must. We only need to adjust the chain length.
perhaps looking into 48V power supplies wouldnt be a bad idea? Effectively driving 4x12V chains in series. I imagine the lower currents in the PSU and lower change in voltage may give good efficiency and perhaps lower cost.
for smaller miners though, 12V pcie connection is best. hobby mining isnt really meant for anything under 300W anyways, and there are some good, cheap 450W power supplies available in most countries