@fpd2dc,

You have a few options depending on what features you want to take advantage of. You can see the full comparison between the modes here: Difference Between Router Mode and Access Point Mode on Deco

In AP mode, many of the network management and parental control features are limited, as they will be controlled/managed by the router portion of the verizon gateway. You can set the AP to use the same SSID as your main network, which will result in one visible SSID. 

If you want to use the Decos Advanced Features, you need to configure the deco in router mode and disable the wireless and routing functionality on the main gateway. Having two routers on the network will cause conflicts with how the IP addresses are assigned and will cause issues with connectivity, so you should always only have one router on your LAN. You will need to first look into whether bridge or passthrough mode can be enabled on your gateway, as there are a few Verizon devices that do not let you do this and require the use of AP mode