If you are going to use encryption or security then numbers of clients supported per AP will take a hit.
No AP goes beyond 500 whether with encryption or NO encryption. If VOIP is being planned to be used then SIMULTANEOUS VoIP CLIENTS is Up to 60 (802.11e/WMM support), 30 per radio on 7982. this is as per datasheet which can be found here:
ZF7982 & ZF7372 are both dual band concurrent AP's,
By default whether in a standalone mode or controller mode, both AP's are configured for concurrent 2.4GHz and 5GHz operation.
60 is a max number for concurrent VOIP client supported on ZF7982 so roughly 30 on each radio.
If there is no VOIP and security then ZF7982 can easily handle 80% to 90% of numbers advertised. I don't have proof however i have seen it handle then well.
I have recently deployed an HD WLAN and found that an AP can take at least 270 devices, however I wouldn't recommend it as the retries do go up quite a bit beyond the 150 mark. Try using the 7372-E with a directional antenna for HD and limit the size of the cell to not enable more than about 100 to 130 devices per AP.