So, you're aware the AP's do have a bit of magic to them, We are covering the below space (marked with an A) with only 13 APs. The building is 3 stories above ground, 1 below. with a bit of coverage external in the rear due to programming concerns with vehicles which are "dead on arrival". we placed our APs based off of Heat maps we built a few years back. This setup provides reliable access to 190 client devices. in our most mission-critical areas, we use R710-R720's. these APs are absolute ROCK STARS when it comes to high-density areas where we have to provide ROCK solid client performance to our employees who meet, greet, write service on the Wi-Fi.
We have another site, which is more open and in a far less dense metropolitan area which gets away with just 4 APs at the
it has 3 fewer floors, and we support less than half the clients, and we have a different customer reception strategy ( where the clients aren't greeted by a Service Professional with both diagnostic and a surface pro on their hips)
In closing, I'm unable to speak to what your experience may be(And, I'd hate to accidentally give you bad guidance), but I am able to show you two examples of my own. I hope that helps you somehow.