Bluedroid is a stack provided by Broadcom and is now opensource in android . Bluedroid is not related with bluez in any respect, it has few advantages over bluez(i differ to that).
[1]. Bluedroid does not have a2dp sink support as of now, as per code available source code only a2dp source support is available
[2]. Audio.conf file is for bluez stack, it is not a part of bluedroid
[3]. Directly calling Bluez API-- i think you will use dbus calls but bluedroid does not support dbus method calls, it has a callback mechanism implemented, so it will not work, bluedroid is not an expansion of bluez.