This is a round about way, but if you connect a pc directly to the modem, it will tell you what it negotiated. NOTE: Probably a good idea to disconnect the cable from the modem that leads to the outside internet (coax if cable, dsl wire, etc.) unless you know your pc firewall is setup to block public IPs.
In Network and Sharing on Windows 10, it will show the connection speed. On linux, at least ubuntu flavors, there are network connection GUIs that will show it.
Also, on the linux command line, you can use ethtool adaptername (usually eth0, but could be something else) to find it. May have to install ethtool. ifconfig will tell you the name to use for the adapter.
The R7000 has gigabit wan. I have had one for years now. It connects to my modem at 1gb as I have gigabit internet and have speeds well over 100mb/s so I know. If the cable modem has gbit connector for the lan, there is no reason why the R7000 should connect at less than gigabit. _________________ -----------------------------------
Netgear R7000