I don't know how technical you are.
b,g, n are the different standards / speeds.
they are backwards compatible, but the issue is the wifi will drop to the speed of the slowest item on the network to be compatible.
most people don't have anything as old as b, but if you do, it drops your speed to that level.

password to xfinity should be different than your password for wifi access. and it shouldn't affect if you can see your wifi ssd.