Hi, I have just purchased the Archer AXE75, and about to install.  The worry I have is that the isp TalkTalk end has a Sagencom modem/ router but does not have an option the turn off the Bridge (I think that's the terminology). I know I can turn off the WiFi and only plug the new tp-link router wan port into the Sagencom Ethernet port. No other Sagencom Ethernet ports to be used.  

I understand the issue is the 'double nat' problem.  Basically both routers wanting to be the 192.168.1.1 ip address.

I plan to set the WiFi ssid and password as in the old router and connect all the Ethernet devices into the Tp-link.

So, to keep my 50+ current devices the same, should I change the Sagencom router to be at 192.168.0.1 for example, and have the Tp-link as 192.168.1.1. If so, how do I get them linked?

Also, I have read things about port forwarding, is this something I need to do, if so what ports.  I do have cctv, so I suspect that's where this might be important.