@DaBoo did this in his app and user’s don’t need to put the details to signup.
You can check the app here : Drunken English: Second App Finished
You can have a screen like welcome screen ( the screen that user see first ) and add a button and add the Signup action and fill the email,password and id ( a number property ) fields with values.
For the email you can add like user,guest and you can add custom formula that you can add all users > max +1 inside it ( you need a number property on the Users collection like ID to get max ) and you can add @gmail.com. ( guest1@gmail.com , guest2@gmail.com ) For the password you can add guest with that all users max formula. And you can add a link action to Home screen. After if the user needs to update the profile you can add a form with the Update Logged in user option.
You can check this topic created by Colin too : Guest to User flow tutorial
Thank you