Yes, start VRChat in the Steam interface (press the left controller menu key and pick your library, then select VRChat and “Start in VR”), do not start it in the Oculus menu if you plan to play with Driver4VR for that play session.
The reason for that is because Driver4VR uses OpenVR Input Emulator to add the “fake” body trackers, and the Input Emulator relies on SteamVR to be open. So any time you want to use Driver4VR full body, start it in Steam instead of Oculus.