Router/Modems

Six months of AT&T crap is making me ripe for a new provider.

Looking at Spectrum. Supposedly Fiber in my area and cheaper for faster
internet and phone too. They will take over and allow me to use my
current phone number.

But, they provide only a modem unless for $5.00/month they provide a
Netgear N900.

I would rather make them responsible for a modem/router that use mine.

However, the big question in all of this is how fast is their WiFi
electronics ?

I run Amped WiFi Ananlytics inSSIDer (free tool) on my PC and see that
the AT&T WiFi speed is less that "Max Rate" 200. People around me have
faster WiFi speeds.
I have a high power modem/router that has demonstrated "Max Rate" 600 speed.

This speed seems to be an internal speed of the modem/router and the
ability to handle multiple wifi signals quickly.

Can someone explain "Max Rate" better ?

And how do I find this speed rating of the Netgear N900 ?

And what is the power rating of the N900 ?

My Amped modem/router is 900 mw power and 500 or 600 speed.