Question concerning Airport Extreme guest account

It is my understanding that I can have a separate network set up for people to use when they are visiting with their macs. Separate account allows them access to internet without giving them info about the network that is set up for my family's personal use.

The question is if the guest account user only has b or g capability for networking purposes, will that then slow my n network from n to g or b?

Welcome to the Forum. Yes you can, if you have a Dual Band TC or Extreme but you must have same Network name for both bands and there is no control over bandwidth usage. But it can be with or without a password. My understanding is the Network runs at the speed of the slowest device. But you may be able to lock in into 11n - not sure.
But you cannot have a guest account if you have bridge mode selected under Internet/Connection Sharing

This using set up assistant;


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