Help setting WG VPN between Fritzbox server and OpenWrt (LAN to LAN)

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello community,
I recently managed to install OpenWrt on my ZTE MF289F, used as LTE router. Everything works very well so far and really happy with it :slight_smile:
Internet is provided by QMI cellular interface.

Now I would like to set up a VPN connection to a "Fritzbox-made" WG VPN with this setup:

Fritzbox network:
192.168.10.xxx

OpenWrt network:
192.168.20.xxx

I would like to have devices on both networks be able to essentially communicate, so that I can use smb/ftp between them, so that any device on network A (192.168.10.xxx) can talk to devices on network B (192.168.20.xxx) and the other way around.

I configured the server on the fritzbox, using the webGUI, essentially selecting the option to "set-up a LAN-LAN connection between this Fritzbox and another Fritzbox or 3rd party WG router". Here is the wg_config provided from the Fritzbox:

[Interface]
PrivateKey = ***
ListenPort = 57994
Address = 192.168.10.1/24,fdc4:e84e:cfcd::3ea6:2fff:fe42:df9b/64
DNS = 192.168.10.1,fdc4:e84e:cfcd::3ea6:2fff:fe42:df9b
DNS = 192.168.20.1,fritz.box

[Peer]
PublicKey = ***
PresharedKey = ***
AllowedIPs = 192.168.20.0/24
PersistentKeepalive = 25

then, after the setup, it allows me to download the conf file for the client, which is as it follows:

[Interface]
PrivateKey = ***
Address = 192.168.20.1/24
DNS = 192.168.10.1
DNS = fritz.box

[Peer]
PublicKey = ***
PresharedKey = ***
AllowedIPs = 192.168.10.0/24
Endpoint = blabla.myfritz.net:57994
PersistentKeepalive = 25

I used this second config to set the WG interface on the OpenWrt, needed only to remove "DNS = fritz.box" beacause it was not accepted as valid.
The WG is apparently up, confirmed by Fritzbox (it is active and refreshed correctly) and confirmed by OpenWrt too (up and connected) but I would like to ask you if anything is missing.

Then it comes to the firewall zone and forwarding thing. I read some other threads on this forum about similar configurations but I am now really confused on what should I do with the firewall settings, what's the correct way to assign zones and forwardings.

Thank you in advance