I wanted to follow up on the 2-cell version of this new board. I finally got around to buying this one:
https://www.ebay.com/itm/186079016381
It has two 18650s in parallel (or you could just have one), and uses what seems to be a popular Chinese meme of having multiple parts in parallel. So it has two schottky load sharing diodes, four P-channel mosfets, two battery protection chips, and two electrolytic output capacitors, all of which I assume are intended to deal with the increased current.
Like the single-cell version, this one has no output connector, such as a type-A socket. But unlike the single-cell version, this one has plenty of input capacitance on both USB power and the batteries. Another difference that I think is important is that the 2-cell version makes no provision for an on/off switch just ahead of the boost converter. So the only way to stop the battery from powering the converter is to remove the batteries. That's not something you want to be doing. I may see if there's an easy way to deal with this problem by cutting a trace and installing a switch.
I tested the charger portion, which worked fine, but haven't done any high-current tests or protection tests. It does work fine as a UPS, with no glitches when USB is connected or disconnected, and of course no minimum current requirement to keep it running. It is not a power bank.