Xfinity Gateway Functionality with Voice

We've been Xfinity Cable Internet customers for years and are now thinking of ditching our AT&T POTS landline and replacing it with Xfinity Voice using either a  Netgear CM2050V Modem or an Xfinity Gateway. We want to keep using our current Assus Router. This article along with other posts I've read says it would be possible by putting the Xfinity Gateway into bridge mode.
But, during a chat with Xfinity a moment ago the agent said, "Xfinity gateway does not work on bridge mode".
1) Is this true?

He also said we had to port our AT&T POTS Landline number when we signed up for Xfinity Voice. We could not transfer it later.
2) Could we order an Xfinity Gateway that supports voice, make sure it works with our router, and sign up for Xfinity Voice later including porting our current landline?

We asked what Xfinity Gateway models could we potentially get so we could check out the features and manual.  He told us since we are using our own router we could not get manuals of Xfinity Gateways.
3) Is this true?  Is there a way we can know what we will be receiving before we order it?

We also were thinking of buying a Netgear CM2050V Modem  instead renting the Xfinity Gateway because it would be much less expensive and we don't need the router portion of the gateway. But, we've heard of firmware issues with the Netgear CM2050V and the potential of it being discontinued. If the Xfinity Gateway doesn't have the bridge feature, we may have no choice but to use the Netgear CM2050V.
4) Any customers care to share recent pros and cons of Netgear CM2050V compare to the Xfinity Gateway? (I believe for a while uploads speeds were problematic, but recently matters seem to be better.)

Finally,

5) How satisfied are customers using Xfinity Voice with the Gateway compared to their satisfaction with POTS landline or cell service?

Thanks much in advance.