Is it possible to return a User Model Entry or userid from a successful registration form submission?
In your redirect hidden input in your form, add an {id} tag like so:

&lt;input type="hidden" name="redirect" value="nextStep/{id}"&gt;


And that will be populated with the newly created user's userId.


  Is there a corresponding getNotices() similar to getErrors() or some way to retrieve these on the front-end?


You'd have to duplicate the code that the control panel uses to retrieve the notices on the front-end of the site.