DHCP pool for overlay same as primary network

tl;dr: what should the primary and overlay network DHCP pools be set to when using DHCP mode with the overlay network defined to be the same subnet as the primary?

I've had to switch Firewalla to DHCP mode to try and get some stability on my Hitron CGN3 router. I originally set it up in simple mode, which worked fine for two weeks, but for some reason now causes problems with the router (wifi drops, no connection to the internet).

I saw on https://help.firewalla.com/hc/en-us/articles/360021737793-How-to-keep-your-network-unchanged-in-DHCP-mode- that I could use method 2 and make the overlay the same as the primary network. I had originally set the overlay to the default, but this eventually caused the router to apparently malfunction.

The link above describes how to set up the overlay network to be the same as the primary, but I think perhaps the pictures are out of date: on my Firewalla app I see the primary network settings have a DCHP address pool, which is not pictured.