Just to let you know while Guest WiFi does offer isolation be aware that many don’t offer full isolation so if security was a concern you need to check you can’t find a device on a separate network. For that you might need to move into enterprise level gear for full layer protection depending on how much you are concerned about access to your main network.
An example would be you have IoT devices and want to completely isolate them, you would need to insure the firewall rule is applied to that network if the router has the ability to secure that. Most domestic routers guest WiFi stops basic access but not full access, I’ve bypassed every NG router I’ve tried including their latest AX routers but to be fair it’s not meant to be overly protective as understanding Firewalls and layers or monitoring of devices is above a domestic router.
Isolation can be done via an AP too, for example NG EX8000 has settings to allow access to main group via its firmware ie access to the routers login for admin so you need to confirm that via firmware but again it’s not fully isolated.
