Is it OK to use an 863 Mbps Netgear C7000 on a 1.2 Gbps plan?

​Hi,​

​My friend wants to use a Netgear C7000 modem/router combo on a 1.2 Gbps Internet plan, the C7000 has a max speed of 863 Mbps.​

​800 Mbps is fast enough for their needs & the renewed Netgear C7000 price is right.​

​Can I assume the only negative will be max speeds of 863 Mbps instead of the full 1.2 Gbps?​

​At the top of the Device Support page it states "​​make sure you purchase a device that has a download speed that is faster than your current Internet plan speed​​." So, if we don't do that, what happens?​

​Is Xfinity going to tell us we can't use that C7000 because it is ​​incompatible?

​Thanks​