I'm not very versed in WiFi technology and jargon, so please keep this simple. Suppose you have an item that you don't want to give access to your main WiFi network, for security reasons. Suppose further that the device, per the manufacturer, will not work with a guest network. One option might be to get another router, connect it by ethernet to your internet provider's modem and create a separate network just for the item.
A couple of questions:
o How would that compare to using a guest network?
o Could the device or app get access to your main WiFi network, assuming some devious software?