Do you have a laptop or desktop? Open your browser and go to 'speedtest.net' or 'speedof.me' and do the test. You can do the same with your smart phone- same addresses.
If you have smart outlets/switches, a Dyson (or similar) vacuum or many other devices that connect to WiFi, get a different router- the Spectrum WiFi 6 tower A) only has three ethernet ports, B) can only be adjusted using a phone app and C) the 5GHz band can't be turned off in order to connect those smart devices.
Some devices can connect, but it's not as easy as if you can turn off the 5GHz band and use the 2.4GHz band.
Nothing new comes with g or b (802.11b, 802.11g)- they all come with at least n speed. Don't sweat these details, just make sure the router is placed in a central location in the house and not in a corner of the basement, behind the furnace or other things that can block the signal. Hardwire EVERYTHING that has an ethernet port- wired is for performance, WiFi is for convenience.
I have been using EERO routers- they use an app for setup, but it does a whole lot more than the Spectrum router (you can only change the network name and password), you can turn off the 5GHz band and it will go back to normal in fifteen minutes. You can use the app to monitor the network, block devices, reboot/turn it off and perform updates if you don't like those happening automatically. Also, you can use the app to run a speed test or see the speed over the previous days. If you need to cover a large area, these work great because they form a 'mesh' network, which is kind of like having a group of people holding hands, then shaking one of them and causing the others to move in response. Roaming is much smoother than with many routers (especially if you have an iPhone) and you can set it up as an access point if you want to keep the existing router- you do need to put it in bridge mode, but it'snot hard to do. If you want help, you can call their tech support number (it's shown in the app) and it doesn't take long.
The new Spectrum hardware is better than a lot of it was, but it's not as good as EERO and some other brands. When I do speed tests on EERO WiFi, I see the speed being paid for- that's not what I used to see with Spectrum routers, but it depends on how new it is. I have the WiFi6 and it's decent- the WiFi speed is generally over 200Mbps, so it's definitely better than what I had before.