Noctua NF A12x15 PWM fans
pros: quiet, perform well, slim 15mm, rubber pads and mount, quality
cons: brown color
If you plan to include fans, I vote for PWM and slim profile fans regardless of the brand.
Honestly if you look at the M1 case internals, there is some space above the Mobo and PSU that can account for 15mm or so within the case's current design also if you removed one of the three PCIe slots and shifted the entire rear IO down a slot there is additional space for a top mount. This...
I have been observing your creations step by step and really like your simple elegant designs. I currently have a V5 M1 almost completely built except I'm waiting for the 7800k to arrive. I have fitted the m1 with a GTX 1080 FTW Hybrid (requiring short cables) as the pcb is longer then reference...