I know that Raspberry Pi's use Bluetooth 4.1 which is low energy. But looking back at Bluetooth 3.0 classic, it can transfer files at an speed of 25Mbps. It also mention that it uses wifi-direct to do that. So when I look at raspberry Pi, I see only an speed of 64Kbps which is no where near the speed of classic 25Mbps. Now is it because it is using BLE. If so, is there a way of changing it to bluetooth classic, so that I can obtain higher transfer rate via bluetooth?
Bluetooth 4 and Bluetooth 5 both use Bluetooth Low Energy (BLE), also known as Bluetooth Smart. They are not able to be switched to "Bluetooth Classic". Bluetooth Classic refers to Bluetooth before 4.0. All 4 and 5 Bluetooth devices are BLE only.
The reasoning for this is the focus on optimizing bluetooth for single-device, low bandwidth connections to take less energy. If you're looking for a faster method, I'd recommend WiFi Direct.
I am also investigating the speed of bluetooth transfers between raspberry pis, in particular the 3 and the zero which both have bluetooth 4.1. My max speed is currently at 80kBps (kilo Bytes/s).
Im not sure if there is a way to switch between bluetooth classic and ble but if you're using RFCOMM to communicate between the two, that is not supported on ble so you must be using bt classic.
So depending on which protocol you're using, you can figure out whether you're using ble or bt classic?
ps. did you get any further with increasing your bandwidth?