AX4 (RAX40) setup with Existing Orcon Router NF18ACV

Right can someone please help as this is driving me nuts....

I purchase the Netgear AX4 4 Stream Wifi Router (RAX40) to provide wifi 6 connectivity through-out the house in conjunction with the Netgear MK63 AX1800 mesh system. Configuring in conjunction with my existing RSP/ISP modem router a NF18ACV is proving to be a nightmare.

Ok on the NF18ACV i disabled DHCP and then connected the new AX4 hoping to provide it with a static IP on the same IP range reserved in the NF18ACV. Then i discovered you can't have the same ip and subnet as the 192.168.1.1 range as the Orcon NF18ACV.  When I connect the ethernet cable from the NF18AVC to the internet port of the AX4 i can get internet connectivity via the wifi but not via the ethernet and when you run diagnostics it complains about the DNS server not being able to be found.

What is the correct method for configuring two routers one which is your RSP/ISP gateway device and the other you wish to put all other lan traffic through and us for wifi 6 and the mesh?

The default private addresses on the Orcon NF18ACV are 192.168.1.1 sub 255.255.255.0 

Can anyone help? I even tried to set the AX4 to a different subnet 192.168.10.1 to about the IP port conflict but still not connecting via IP or allocating the IP address via the netgear.

All help appreciate

P.s. all latest firmware and both devices have been updated. Orcon saying they can't provide technical support to help with third party devices...typical especially as they don't offer a wifi 6 device

Help....