Initial set up

cdsatpb wrote:

A very basic question: does the router in an Orbi mesh system connect to the ISP router, or does it replace the ISP router?

There's no single answer to that.

You can use it either way. You don't say what Utility Warehouse router or which Orbi system you have. 

Unless it does things that the Orbi can't manage, the easiest and least complicated option, is to get rid of the other router. Then just connect the Orbi to the FTTP terminal.

If you do need the other router for some reason, you then have to avoid the "two routers" issue.

What is Double NAT? | Answer | NETGEAR Support

One way to avoid that is to put the Orbi router into access point (AP) mode.

How do I configure my Orbi router to act as an access point? - NETGEAR Support

but then you hit this:

Disabled Features on the Router when set to AP Mode | Answer | NETGEAR Support

You'll have to work out if that blocks things that are important to you.

I'd start leaving the Utility Warehouse router gathering dust on a shelf somewhere.

Just another user with time on their hands.