1. I have a guest network. And I want to limit the no. of users of that particular ssid in whole wifi network, let say limit max. 500 clients for Guest SSID.
2. I find that there is a setting "Allow only up to 100 clients per AP radio to associate with this WLAN" I am not sure it means? A: 100 clients * 1 SSID * 10 APs * 2 radio(2.4GHz+5GHz) = up to 2000 clients B: 100 clients * 1 SSID * 2 radio(2.4GHz+5GHz) = up to 200 clients(no matter how many AP) or both wrong.
That limit applies per AP not the WLAN. [I'm referring to a ZD environment.]
There is no maximum configurable number per WLAN (with the exception of your example 1). Your limit is the hardware in your environment and will be modified for instance by ACL MAC address space allocation (if using) or type of encryption (impacts back on hardware though really).