I think that your choice of number of APs, channels, and how you handle the backhaul will be much more important than the specific devices you use. There are many opinions and recommendations in the long thread
"Central management" isn't something that OpenWRT has focused on, typically being used by individuals with a handful of APs at most. I'd suggest looking at rsync and some shell scripts to "customize" the options for each AP.
I'm assuming you need that many APs for sufficient signal strength over the area, not as an attempt to increase throughput.
With that many APs in a relatively small area, you'll need to apply enterprise-style channel allocation to reduce the impacts of the APs colliding with each other. That is the nature of 802.11, not the AP hardware. Both beacons and the communication itself will collide, potentially reducing your overall throughput significantly.
See, for example