Netgear LM1200 Failover settings

In my situation the Orbi RBR850 is executing a DHCP request with a reservation on the Ziggo Connectbox. It will get 192.168.178.10.

The Ziggo Connectbox has 192.168.178.10 in the DMZ.

The Ziggo connectbox is connected to the WAN port of the LM1200

The Orbi RBR850 is connected to the LAN port of the LM1200

LTE is working fine on the LM1200 if tested with a laptop on the LAN port.

My questions are;

- To use the LM1200 in failover mode, should I put it in router mode or in bridge mode?

- Will the Orbi RBR850 still be able to do DHCP to the Ziggo Connectbox (is DHCP passing through the LM1200)?

- What IP-adress should I give to the LM1200, preferably I would like to give it 192.168.178.2 but will that work?

I am sorry to ask these questions, but I was unable to find answers in the User Guide.

Regards Leo.