Google WiFi and Google Nest

Maybe. I guess it depends if you plan on upgrading some of the pucks eventually.

The nest wifi router has the better hardware and capable of better speeds. But if you are going to keep the old pucks with it, then I would imagine you'd be hampered by that anyway. So I'm not sure what utility you gain by upgrading the router in that instance.

Additionally it's the nest pucks that have the speaker/mics. The nest router doesn't offer any additional capability in that regard.