Can I use wifi router as a switch?

> All done. [...]

   _What_, exactly?

> I am worried that the status says DHCP ON

   I'd guess that that's accurate only if the router is acting as a
router, not when it's configured as a WAP.

> The Genie offered to use the Netgear as an AP

   After a settings reset, if it sees a private address on its
WAN/Internet interface, then it might draw the correct conclusion
automatically.

> I kept SSID broadcast on recommendation. [...]

   That doesn't matter much if the radio is disabled.  The point was
that "Enable SSID Broadcast" and "Enable Wireless Router Radio" do
different things.

> So DHCP organises the different ports? [...]

   I'd say "connected devices", not "ports".

      https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

> I had problems in the past with WAP acting like a router and
> distributing weird IP addresses on our network.

   Generally, you want one DHCP server per LAN.  Multiple uncoordinated
DHCP servers can cause many problems.  Which is why the one-step WAP
mode option disables the DHCP server.  (And, why you would need to
disable it explictitly, if you don't use the one-step WAP mode option.)

   So, it works as expected now?  (What could go wrong?)

   Possibly interesting:

      https://kb.netgear.com/26765