The portal users who are authenticated from the admin side can directly login to the portal using the credentials.
Here the portal users will get the login page widget as configured from the Design -> Page Builder admin side.
If reCaptcha is enabled, the portal user will get the reCaptcha option at the time of login.
Note: You can allow the portal users to access some of the menu/pages before login. On the login page, you will get the option from the header menu, as you have configured it as before the login page in the Page Builder.