Ok I have done this and currently it's working fine, but currently my OpenVPN config is up and running, but my traffic is not going through it automatically, anything that I should do?
You have configured the device as a dumbAP. The other lan hosts are using the ISP router as gateway. If you want them to use the OpenWrt as gateway, you need to disable dhcp server on the ISP router and enbale it on the OpenWrt
I only want devices connected to this router specifically, WiFi and LAN to use the internal OpenVPN server, for all the other devices I do not want them to use this router as a VPN.
My main ISP router is connected to 2 modems right now, 1 as purely dumb AP and this, which I have installed OpenVPN on to and pass through traffic.
I have followed the official guide to make a tun0 interface etc but they won't pass it through the VPN.
How should I do that?
Then OpenWrt must be in router mode, not bridge as you were trying to achieve earlier.
Reset the router to defaults, connect the upstream cable from wan port to the ISP router, setup your vpn, and connect the hosts you want to route via the vpn on the lan ports of OpenWrt.
But I can keep the original IP I have for for the router right? But it must have a DHCP server of it's own am I right? And what does "connect the outstream cable from wan port to the ISP router" means? Connect the LAN cable to this modem's WAN to the main ISP modem's LAN? And will making it in router mode make even WiFi passing through the VPN as well?
I don't understand which one is that.
By default the wan interface uses dhcp protocol. You can either reserve an IP from the ISP router, or switch to static protocol and use the IP you wish.
Yes, it must serve dhcp on the lan.
Correct.
Correct.
Make a new network for VPN users. This is like the locally routed guest network except the vpnuser network will forward and NAT to the VPN tunnel instead of to the direct Internet connection.
Meanwhile the original LAN network remains bridged into the house main network so it has direct non VPN access to the Internet.
I meant like if I change it to router mode with seperate DHCP servers, can I still make the router accessible from a normal network? As I'm currently running a sambashare on it, so was wondering if that was still accessible if it has its own DHCP server
Yes, the samba share is not connected to the dhcp server. Surely the automatic discovery of the shares will not work over the different networks, but you can access the shares by defining the IP.