tp-link x75 pro

I think about the best you can do with Xfinity gear is disable the SSID broadcast if you don't want to see it.  This may work still depending on what exactly you have, and if they haven't removed the option in firmware: https://www.xfinity.com/support/articles/hide-disable-in-home-wifi  .  There might be a setting in the phone app too, but they don't document the phone app.

You can't actually disable the radios in their gear.  The security system one will always be active.  You might be able to shut off the public hotspot for a while, but people report it turns itself back on.

At a glance, your tp-link mesh may or may not have features like DHCP forwarding, where you disable the tp-link DHCP server and forward those requests to your gateway so the gateway still does the internal networking (more of an AP mode).  It's not listed in their app from what they publish.  Perhaps it doesn't work that way with the mesh system.  Dunno.  

You could set bridge mode on your gateway so it's a pass-thru device.  That disables the regular SSID (not security or hotspot), also disables MoCA, and the internal LAN DHCP server.  Then the tp-link then gets the external IP address for the WAN address.  I don't know if you want that to be public facing or not though.  You'd really want a dedicated firewall in front of that.  It makes no security claims, so it probably doesn't have one.

Perhaps you can find a better manual, with the specific model number for what you have to see what other features it may have.

Hello, @rodger.p. Thank you for reaching out over Xfinity Forums for assistance, you have contacted the right place for assistance. If you're wanting to use another devices, and xFi modem as a router, you would want to set bridgemode up on the xFi modem. Here is a great article that has a walk through if you haven't used bridgemode on our equipment: https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode.