Wifi Guest Security

I have the Xfinity Modem Router and I am about to get rid of it.  I feel extremely unsafe about the fact that there is no guest network.  I had someone in tech support at Xfinity tell me that if I give a guest, as in someone I don't really know well,  my QR code that would be safe and there is no way they could access my password.  Also that my wifi network would be safe.  Then I read conflicting information that it's not safe to do that, that the QR code can display my password, and the person I give it to has full access to my WIFI network without my password.   What is true?