Officially sucks! It appears if you have one bar of cell service that will carry the call. My wife has an iPhone and that seems to know to wifi the call even when there is some cell service. So, it would be nice if I could turn off the cell radio when home so wifi would be used. If I go airplane mode and then turn wifi back on it says I cant make a phone call with airplane mode turned on. So, wifi calling on the Droid Turbo 2 is useless...way to go Motorola and Verizon!
As a workaround you can use the Google Hangouts dialer for Wi-Fi calling on your phone. It doesn't fix the core issue, but it does work well.
Yes they will either have to call you using your Google Voice number, OR you can configure your Google Voice settings to forward the call if the cell number is dialed.
Oops, was wrong about forwarding through Google Voice. The call will have to be forwarded through Verizon using either;
*71(call forwarded if no answer)- I suggest this one
*72 (immediate forwarding)
There is no charge for call forwarding with unlimited talk plans.