We don't have voLTE or voWiFi, so we can't answer this. The LG G8S sons works flawlessly

Theoretically, it should work.
I have a MBudget (Swisscom) subscription and can activate it in the settings.
However, no icon appears in the status bar, which means for me that it doesn't work.
Maybe you should ask Sunrise if it works with Digitec Connect...