Since you're on 1Gbps service, you already have Ethernet WAN. There is nothing to be switched.
Your current equipment will continue to work. The new Verizon router has WiFi 6, which is faster. Some report it has better range. I've not tested it. The old extenders to not work with the new router; you would need to upgrade it, too. If you're happy with your current WiFi speed and range, I recommend you stay with your current equipment.
There are lots of VoIP choices out there. Ooma is decent, so is Vonage. If you're willing to do a little more work and configure your own equipment, Google Voice and other providers offer even lower (if not zero) costs.