@KurtP 

I'm afraid not; if the ISP modem works as bridge mode and no wifi and no DHCP server, the devices connected to it won't be able to get internet;

For the wifi AP which can be a wireless router, we can configure it as the router mode with the configuration parameters given by ISP to get internet, while for the device(computer) which connects to the ISP modem, there will be no internet access.

You can connect them like ISP cable--ISP modem ( wifi off, DHCP off, bridge mode--router (wifi on DHCP server on, router mode)---computer/smart phone.