Using Orbi In AP Mode

This question has several components.

• Yes, it is definitely possible to connect another router to one of the Orbi LAN ports, which will force every device connected to that router to pass through that one Orbi LAN port.  I personally have stacked three routers that way (as an experiment), and it certainly works.  But....
• Every router creates an IP subnet for all the devices connected to it.  For example, suppose there are three routers:
  • Router 1 will create an IP subnet, often 192.168.1.x.  Every device connected to this router will have an IP address starting with 192.168.1
  • Router 2 will have one of those IP addresses.  It will create a different IP subnet for every device connected to it, usually 10.0.0.x
  • Router 3 will have one of those 10.0.0.x IP addresses.  It will create an IP subnet, usually 192.168.1.x, so every device connected to Router 3 will have an internal IP address of 192.168.1.
• Each of these routers will use Network Address Translation to tunnel traffic from its LAN devices. so
  • Every device connected to Router 3 will appear to be  coming from IP 10.0.0.x (Router 3's IP address)
  • When packets pass through Router 2, they will appear to be coming from Router 2's IP address, 192.168.1.x
  • When packets pass through Router 1, they will appear to have the public IP adddress of Router 1.
• If any of these routers is placed in Access Point (AP) mode, it will no longer create a new IP subnet, nor will it NAT traffic passing through it.

It remains unclear (to me) what the goal is. Most people who have up to 5 devices they want to use a VPN simply install VPN software on the device itself.