New Orbi RBK753, want new modem...need help

I have just installed a new Orbi RBK753 system. It is working very well.  It is fed by a three year old Arris Docsis 3.1 Surfboard SB8200 cable modem. I have Comcast/Xfinity Gig Triple Play service.

Our voice modem is an old Arris model, no longer supported, and giving us trouble for home office phones. So, our thought is to get rid of both Arris modems and purchase/consolidate into one new Netgear CM2050V for voice and data.The CM2050V is billed as a 2.5Gbps cable modem. 

I am wondering about the available speed capacity of the new Orbi router. Does anyone know what the max capcity/throughput is?The specs show "1 GPS Gigabit Ethernet WAN port". Is this accurate?

Our current Xfinity Gig service plan tops out at 1.2Gbps. If I own a new voice and data modem for a few years like I usually do, the likelyhood of higher speeds from Comcast is almost a certainty. Can I assume the upstream and donwstream speed compatability to be at least 2.5Gbps of a new modem, or will we top out at 1Gbps because of the Orbi router?

Thanks for your help.