Hi there!
Thanks for contacting us.
Yes, you can use SP Pge Builder to create both pages, and articles, no problem.
Article details page can be designed by SPPB editor, but it can not be edit your existing content that was made with the default Joomla editor. There is no default way to migrate the contents from the Joomla editor to the SPPB editor. You have to do it manually copy/paste method if the content allows copy paste feature.
With a akeeba full site backup, it includes SPPB pages also, yes.
Best Regards