How to let user open two different screens given different response

Fred, could you provide some details, feels tricky but I feel it could be achieved in a different manner, wanna try to help if possible.

This can be done using state pages: https://www.youtube.com/watch?v=o4eChy6GrS4

but how do I setup custom state pages from Xano? Is error 404 for istance would be a function returning only the number 404?

The 404 is a status code. It is unaffected by the content. Check it out here: https://docs.xano.com/api/the-basics/api-status-codes
I'm not sure about how to force a status code using Xano though but that is something that they can easily help you with.

Using Conditional visibility

I watched the video and I perfectly understand I can bind screens to error status pages or empty lists or other statuses that are part of HTTP response exceptions. What about all the other cases? If I want to bind a page not to an exception but to a certain variable value, is inducing a status error code the only way to bind it with Bravo Figma tags? 
In the example there is also mention of binding the screens to role access, but that part it doesn't get explained

The roles would work the same. For example: An admin would return the status code 123 and a normal member 124. The code number would basically replace the variable.

right! Okei I'm gonna try it

I'm going to DM you another tutorial where I explain the user permission block a little closer.