Hello @peter79
The Nest WiFi Router unit can be configured in "bridge" mode. However, in this mode it will not support adding secondary units to expand the coverage area (you would also lose a number of other features, including Guest WiFi, prioritization, and more). Running with double NAT can be an issue in some cases, but doesn't cause problems for most people.
Wired backhaul of Google WiFi units (or additional Nest WiFi Router units) works quite well, but they all have to be connected to the "inner" network created by the primary Nest WiFi Router (or Google WiFi) that is connected to your internet service. Using an inexpensive unmanaged Ethernet switch to build a network to support that from the LAN port on the primary is recommended. Note that wired secondaries are not supported if the primary is in bridge mode – the wireless mesh connection is still running as a backup and managing all of them as a group requires the primary to be in router mode. I'm a little unclear on what you're asking in your closing question, but I hope the above answers it. If not, please don't hesitate to ask for clarification here!
