DASBOOT, thank you so much for helping me get out of limbo.
I thought that if the main plug is called a 24 Pin ATX connector, then this would be a 2 Pin ATX, and that got me stuck. I can see now the right name is Molex Mini Fit 2 Pin. It's always a nuisance to get that right.
Note the Q170T is a 19V board, and I doubt it is 12V (co-voltage) as some Thinitx boards will accept either voltage at the 2-pin molex.
From the manual, I can see that the external barrel connector accepts both 12V and 19V. There is no mention of voltage on internal connectors, so I cannot be certain, but I assume if the external is dual voltage, internal should be as well. There is contradictory evidence about it out there on the web, so I'll have to buy a board and see.
I'm new to Thin ITX stuff, but what hit me is that I suddenly don't need 24 Pin plus 8 Pin to supply power to the board, just two tiny pins, and that's all. So why even bother with all those cables if it can be sorted out using just two? I've looked, and my PSU says that it can provide 12V at 17A, which gives over 200W, and that is enough I many use cases. It feels like I need to explore more of that topic.