Hello @Mselim
The Nighthawk R7000P appears to be a router + firewall + WiFi access point. It's not a modem. So, if you are currently using it, you must have something else serving as your internet connection already. At least some fiber internet service providers use a separate ONT, which is pretty close to being just a "modem" for optical fiber, and would have an Ethernet connection you can connect a standard router (like your Nighthawk) to. However, AT&T appears to only support their own combination ONT + router + firewall + WiFi access point device. It does look like you can configure that device in a sort of "pass through" mode if you want to use your own router, but the AT&T device will still have to be there (and you'll still have to pay for it). If you plan to use your own router, you will want to at least disable the WiFi access point feature in the AT&T device, and preferably put it in pass through mode as well. Hopefully this helps you better understand the internet connection aspect.
Next, though, we need to discuss how something like Nest WiFi might fit into a system like this. Nest WiFi is also a router + firewall + WiFi access point (that also includes a mesh interconnect feature to expand coverage via Nest WiFi Points, other Nest WiFi Routers, or Google WiFi units). So, it wouldn't make much sense to use it along with your Nighthawk router. I would probably plan on at least testing the Nighthawk in your new home before spending money on something like Nest WiFi. If the Nighthawk doesn't provide enough coverage (and do try to get it placed as close to the center of your home as possible), then you could look at something like Nest WiFi to replace it. But, a single Nest WiFi Router likely won't have better range than the Nighthawk, so you'd want to look at a Nest WiFi package that includes one or two Nest WiFi Point units, or maybe a couple of Nest WiFi Router units. Again, I hope this helps you better understand the router/firewall/WiFi aspect of the system.
