This message was posted on behalf of Intel Corporation
I will try to help you with this. You mentioned the two main Bluetooth profiles that are used to transfer data FTP and SPP. As you said FTP will only transfer files not strings of data. Nevertheless, SPP can be used without the SPP-PRO app and it creates a virtual serial port. If you're interested in using SPP to communicate between two Edisons I'd suggest you to read the following article: http://www.devshed.com/c/a/python/bluetooth-programming-in-python-network-programming-using-rfcomm/ it might be of help.
You will only be able to receive data from BLE devices using GATT as this is the profile that manages BLE communication. So, GATT will only be available for BLE sensors, it won't be useful for other types of sensors even if they use traditional Bluetooth.
I don't understand your third question, could you please explain us what you meant by it?
I hope the information above is useful.