When using Wifi calling, do you see this indicated anywhere on your phone? I have an iPhone 12 as well and with Verizon a little animation in the top right corner of the phone would indicate that Wifi calling is active. I've never seen this since switching to Visible. I do have the Wifi calling option enabled though.
WiFi calling won't work (not even available to turn on) on the Moto G Stylus 2020. It seems the Verizon network blocks WiFi calling on phones not purchased from Verizon. So it doesn't work on retail/unlocked phones. At least in the Moto line. Visible doesn't seem to know this / thinks I should call Verizon to try to work it out.