LAN vs. WAN (Google Wifi to Verizon Router)

I have the ONT going via ethernet to Google Wifi.  Google Wifi is setup as 192.168.1.1.  Prior to doing so, I reset the Verizon router...disabled wifi...disabled DHCP...and gave it another ip on the same subnet.  I set a DHCP reservation in Google Wifi for the router.  I plugged the LAN out from Google into the LAN of the Verizon router.  With this, I currently have internet, tv, on demand, tv app, remote dvr, etc. working.  Yay.

Now, with that said, I meant to plugin the Google to the WAN port on the Fios router because that is what I read.

1. What does LAN to WAN buy me?  (everything seems to be working)
2. Am I going to run into an issue later that I haven't seen yet?