It would be great that when a call comes in and the user decides to answer it on the mobile app if he/she could select to answer it on the carrier network from the start. Instead of the current way of answering call on RC mobile app and then switching to carrier.
You should be able to forward all calls to your mobile device unless you would like to ID which ones are coming from Ring Central. If that is the case you are able to add digit prefixes or suffixes to the incoming caller ID. I have not used that feature but you can find it in your extension settings under call handling > settings.
When you flip to your carrier I believe RC simply forwards that call to your cell number anyways.