APs can be configured in standalone modeso that each Access Point has a different configuration of SSIDs in layer 2?
Is it possible to configure several sites in the same layer 2 subnet?
I would say it doesn't matter if they're stand alone and using different ssid's. Whether they're same site or different sites as long as they're not physically connected through a switch.
@vladi0782 AP's that are in the same L2 domain will communicate with each other and form the cluster and do not have the option for standalone mode. You would need to create another L2 domain.