Apple MacBook Air Vs. Microsoft Surface Laptop
Far far away, behind the word mountains, far from the countries Vokalia and Consonantia, there...
Easy to display a nice signup/register form on your sidebar or your content by use Login/Register Form element from WPBakery Page Builder ( Visual Composer ) or Widget Login/Register Form. This form supports display on the topbar also.
If you want to display register link in this form, you need to enable register function via admin page > Settings > General > Anyone can register.