Actually, you can do that using CSS but that won't be a good option.
SP Page builder works inside the component area only, but the header and footer section are under the template. So you will not be able to use SP page builder to control anything that goes beyond the component area.
If you do not like anything beyond this component area, then for those you can create a module and use it as per your convenience. And to remove those, you can then go to Module section, you will find the menu and log in module there. Also, in default template of Joomla, there are some active predefined module position too.
However, i would suggest you to use our templates as the menu structure of it is better and will be helpful for you. You can also use the Page builder layout packages to build your page.
Hope i could explain it clearly, please do let me know if you have any confusion.