Hello,
You would need to use TCP or TLS transport in order to use the application without enabling the two options from the "Incoming calls" section in Zoiper's Settings menu. However the PBX must support TCP or TLS, otherwise the account will not register. To change the transport, you should go to the "Network settings" in the account configuration.
As for the push notifications support, currently it is not available for the iOS version of Zoiper.