1. This is based on your wireless total traffic througput, in my case I have aggregated all 8 ports to give 8Gbps back to network from WLC. At peak time I can see it is utilized 1-2Gbps of traffic most, but still I have allocated 8Gbps for capacity.
2. Yes, Through AP groups or FlexConnect Groups you can assign selected SSID to perticular set of APs.
In the case of local switching the wireless traffic won't go to WLC. Hence how do we select the number of ports for aggregation. Then I believe, it depends on how many APs are connected to the centralized AP. so per AP how much bw is required or assume I'm going to manage 500 APs, in this case how many ports need to be aggregated?
You can do this by trial&error process. 500 APs will generate a significant traffic figure, you can aggregate 4 ports and simply monitor the Switch uplinks to the WLC. If not enough you can always add the rest of the ports.
That's true, we can always depend on trail & error process. However, just want to know, how much average traffic (not actual traffic) can be generated b/w WLC & LWAP. If anybody read in cisco documents, please let me know. If we figure out this, we can always have calculation before implementation.