Help bridging wwan from wifi client to home network (and add a vpn layer)

I need help in understading some OpenWrt basics. Although i have experince with Linux and iptables, i'm new to these kind of setups.

I need to connect to a remote access point using an outdoor CPE which has the wifi interface and one ethernet interface. It is running OpenWrt.
This connection is the wan connection, which is how the rest of devices will reach the internet.

Then I need to make this connection available to the other clients (computer, phones etc) and for this I have another device, with a wifi interface and three ethernet ports, which will serve as an access point also with OpenWrt running.

Here's an image to better understand the situation. Furthermore, I need to forward all the network traffic to a VPN .

Which is the best setup in this case? The Outdoor CPE will have an IP Address which can be either dynamic (there's a DHCP server in the network) or static if I set it. Then i need to bridge it to the Access Point, which will have its subnet and its DHCP server for its home clients. It also needs to forward all the traffic trough a VPN tunnel.

Can anyone point me in the right direction?

There is a "client mode" guide that explains your options: WDS, relayd, or routed.