Nope, you have it backwards. The Topping G5 connects via Bluetooth to a Bluetooth source, and powers a set of wired headphones. Basically turns any wired headphone into a BT headphone.
There is no good reason to do what you are trying to do. Bluetooth headphones have their own internal DAC & Amp. You can't amplify them any further. You can't utilize a 'different' DAC, or multiple DACs.
If your source does not support Bluetooth, you would just attach a bluetooth adapter to your source.