The maximum theoretical limits are barely worth considering. The better question is how slow are you prepared to tolerate it.
For example, if you are using 80Mhz wide channels, and are hoping to get an actual 400Mb/s of delivered bandwidth, and you want users to get a minimum of 50 Mb/s of bandwidth - then the maximum concurrent connected users sucking bandwidth can only be 8. If you allow for a 4:1 contention ratio, then you will want a maximum of 32 users per access point.
The fact that the access point might be able to support 200 is worthless information - because your WiFi network will be so slow no one will want to use it.
So if you have 90% mobile phones in standby and 10% of laptops working, you can easily have 50, maybe even 80 connected devices on the 5 GHz interface in 80 MHz mode (with a strong signal for all clients). The RSSI is important though, so if you have a connected device with a weak signal (for whatever reason) and this device is also actively creating traffic, then it will be slow for all other connected devices.
It really depends on the traffic patterns. For example we started to use VMWare VDI on wireless. On a 3502i AP this allows some 5-8 clients before the performance gets unusable for the VDI users, while on the 3702i we successfully tested with 16 clients active at the same time (hadn't more test clients to test with). I since also enabled QoS on the wireless (or to be precise AVC, great feature!) and configured PCoIP to be of higher priority than all the other traffic. VDI now even works fine if, a client connected to the same radio is running iperf at the same time :)