Using Dual Bands

Adding a cheap 802.11 b/g/n access point for devices that don't work well with combined signal band steering won't impact your other WiFi network.  It's just a different radio.  A lot of them are "Power over Ethernet" or PoE and your Xfinity gateway doesn't do that.  Save yourself some trouble and make sure it comes with a power adapter. 

Quite a few of them will also let you control the radio channel it works on, and also have a site-survey directly on the Access Point to see what other devices are using.  The one you pick to run on may matter, or it might not.  https://www.lifewire.com/best-wifi-channels-for-your-network-818278 

I'd also keep the SSID different just so you know what you are connecting to, even if it has the option/capability to broadcast the same SSID as your gateway.    

@stevej99

Historically, you were encouraged to use a different WiFi name and password for each band. You then had to choose which band your devices should connect to. Knowing which would provide the best connection and performance was guesswork.

That’s now changed. With the advanced intelligence of xFi Gateways, using the same name and password for the 2.4 GHz, 5 GHz and 6GHz (if applicable) bands lets the Gateway sort out which one will provide a better connection at any given time. You will still have all bands and all the associated functionality, channels and range. However, by using the same WiFi name and password for all, devices will connect seamlessly to the most optimal band at any given time. This is called "band steering."

If you have an xFi Gateway, you should simplify your WiFi and switch to using a single SSID. That is, use the same WiFi name and password for your 2.4 GHz, 5 GHz and 6GHz (if applicable) bands, so you can take advantage of this seamless connection to the best network.

If you don't see the 2.4 and 5 GHz WiFi channel settings (i.e., WiFi Mode, Channel Selection and Channel Mode), it means that these settings are being managed automatically to help optimize your home network and provide the best performance possible.

Using Xfinity xFi

1. Open the Xfinity app and sign in with your Xfinity ID and password.
2. Go to the WiFi tab.
3. Select Wifi Details.
4. Select Edit WiFi settings.
5. Select 2.4 and 5 GHz WiFi.
6. Select Edit next to the WiFi band you want to update.
7. Select the new WiFi Mode and/or Channel setting.
8. Select Save to save your new settings.

Using the Admin Tool

1. Connect to your WiFi network.
2. Open a web browser, go to 10.0.0.1, and sign in.
   
   • If you haven't changed it, the default is:
     
     • Username: admin
     • Password: password
3. Go to Gateway > Connection > Wi-Fi.
   
   • To change your Channel Selection, select Edit next to the WiFi channel (2.4 or 5 GHz) you'd like to change.
     
     • Click the radio button for the channel selection field, then select your desired channel number.
   • To change your WiFi Mode, select Edit next to WiFi Mode and select your desired mode.
4. Select Save Settings.

I can't get vac mop to set up with WiFi. Please help