Regarding the NANO, is there a specific reason to have the mobo and the gpu upside down compared to the Dan A4-SFX case?
I mean the mobo perhaps got to normal position as it was upside down in the A4-SFX actually, but that was pretty fine - could having the CPU cooler below, M.2 on above with the fans on top result in better overall temps? With vertical fins of the CPU cooler (AXP90-X36) the air would go nicely up to be exhaled out by the top fans through the M.2 and everything would receive airflow. With the current orientation, the M.2 does not receive the benefit of the top fans as it's under the cpu cooler.
As for the gpu, having the pcie slot below is probably better for stability and the riser cable would not get in the way of exhaling the air on top on the gpu side either. This can be solved by having the connecton of the bundled riser angeled 90' or even 180' though. For me, this is actually fine as with my model, having the gpu turned on it's head would mean the heatpipes would point upwards, but I'm not sure how this is with the majority of ITX cards (or if this even matters cooling-wise).