OnePlus is not officially represented in Switzerland and therefore access to functions such as Wi-Fi Calling and 5G, which unfortunately both require country-specific unlocks in the software, will probably continue to be blocked. However, there are instructions on forums.oneplus.com to unlock the functions until the next update. However, this will have to be repeated.
No, unfortunately not. However, Oneplus has activated the option, so it is up to the providers to activate it. You would have to ask Swisscom/Sunrise/Salt if something is planned. The devices themselves support Wifi calling and VoLTE.