Having the conflict issue as well. Typically, both ringers go off simulateously, Groove usually shows up first, answering there gives no connection and leaves voice ringing with no apparent way to answer. Hanging up with Groove and answering Voice/Native app on the following screen, the call typically disconnects on the phone (caller may get voicemail).
Adjusting the google voice settings to "always" as you suggest fixes the dial out issue, but not this one. I can disable forwarding to the carrrier cell number to correct this. But, if I do that and go out of the data network, I can't get incoming calls or dial out from my google voice number. Alternatively, I can disable call forwarding to chat in GV and lose the incoming call capability with Groove. Neither solution is great.
This is additionally complicated by Groove not working with my car's bluetooth (silence both ways). This isn't surprising because the car (2007 BMW 328) bluetooth is finicky, but odd since it does work with the Voice/Native dialer. Since I need bluetooth to use the phone hands free while driving, it means that if I have Groove working for incoming calls (forwarding to chat only), I can't use the phone in the car.
This effectively limits Groove to a VoIP outbound solution (while not driving) for me. :-\
The selection screen for outbound calls is perfect. Would it be possible to implement something similar for inbound calls? Or maybe a way to easily toggle the Voice forwarding setting between chat and the cell carrier number from Groove?