Kianoosh Karami published a great article about the throughput on BLE using connection oriented GATT protocol here. To summarize, throughput is quite a bit less than standard Bluetooth, with the max of 16kByte/s on Android and 2.6kByte/s on iPhone 6.
On our AIRcable SuperBeacon in CENTRAL mode you can change the timing of a connection in real time. Using the 'h' command, set the timing interval from 6 (7.5ms) high speed, to 3500 for low power communication. See here.