Hello there,
The functionalities offered in GenerateBlocks Pro and GeneratePress Premium are quite different.
See here for GeneratePress Premium functionalities: https://generatepress.com/premium/
GenerateBlocks Pro: https://generateblocks.com/pro/
Now, with regards to your inquiry, GeneratePress Premium offers a site Library where there are full sites ready to use and modify: https://docs.generatepress.com/article/using-the-site-library/
With regards to GenerateBlocks Pro, on the contrary, the Template Library offers pre-built sections as opposed to full sites: https://docs.generateblocks.com/article/template-library-overview/
Hope this clarifies. 🙂