If you have the Eero set up correctly, you should no longer be seeing your Xfinity network as that should be turned off now. Or do you mean you're connecting to your Xfinity hot spot? (A public wifi access point that Xfinity provides for its customers.) You definitely don't want to be using that as it will be much slower and unreliable, as well as it's a public wifi network so less secure. Definitely connect all your devices to your new Eero network for best performance.