Hi @Damo . If you have FTTP, the Google device should just work since VLAN is not used.
Otherwise, you have to keep the Archer connected to the NBN box to do VLAN processing.
If you use the VOIP phone, the Archer has to be in standard configuration and Google device will be access point.
If you don't want the VOIP phone, the Archer can be put in bridge mode and the Google device will be in standard config: PPPoE, username and password, and DHCP enabled. The Archer wifi can be disabled and just use the Google wifi.
Info about Google device and VLAN tagging:
Have a look at this thread. It describes putting the Archer in bridge mode.
Start from: On the "Advance Tab"