It is better to use wclAuthenticator together with wclOPPClient. But you must setup wclOPPClient.BluetoothParams.Authentication to True. Otherwise it will work incorrect or may not work (depends on Bluetooth driver used). However, if you will set wclOPPClient.BluetoothParams.Authentication to TRUE for all devices than any device will ask for PIN. That is why it's much better to use wclProximitySender to send content to multiple devices.
Any way, I do not recomend to use WCL with threads as it is asynchronous and does not need any thread to send to more than 1 device at the same time.