Regarding the CPU cooler, the AXP90-53 has the best heatsink for tiny 92mm cpu cooler, even if its assembly process is total BS (for my point of view). However, DO NOT USE it with a slim fan (either 15mm native fan of 14mm Noctua) inside the P-ATX. Why? With 10-15mm gap you will recycle hot internal for sure. Forget the fan duck as you can put a 25mm thick fan instead.
@riba2233 is always considering extra space to avoid air turbulence. You would need to use cable ties, metal wire to maintain the fan on the heatsink. Personnally I would prefer using the ID-Cooling IS-53-XT, performing a little bit worse than the AXP90, but with a top notch assembly mechanism, and you just need 30mm m3 screww to fit a 25mm fan...easy to find.