Hi Naghma,
GeneratePress theme along with GeneratePress Premium and free GenerateBlocks plugin should be enough to create a website from scratch.
For instance see this sample walkthrough video of how a site template was created: https://www.youtube.com/watch?v=-rs0E_rIFtk&t=436s
There are also other videos in our YouTube channel you may refer to: https://www.youtube.com/c/GeneratePress/videos
As for the difference, you might find this thread very informative: https://generatepress.com/forums/topic/what-is-the-difference-between-elementor-and-generate-blocks/
Also see: https://generatepress.com/forums/topic/what-is-the-difference-between-elementor-and-generate-blocks/#post-1679263
In essence, the greatest difference would be performance.
Hope this clarifies! Feel free to reach out if you’ll have any further inquiries!