A: Hello! Since you mentioned Elementor, I'll try and drop comparisons to hopefully make things clearer.

You just need the default Twenty Twenty Five theme or any block theme available in the WordPress Theme Directory — this is similar to how Elementor should be able to work with any theme.

As for which is responsible to which, the block theme you pick would control the initial state of how the overall look and feel of your website. You could pick a block theme with more advanced options included, this is up to you, but just even the default ones will be perfectly fine. Nowadays, the default ones are quite robust!

If you've picked a block theme (as opposed to a classic theme), Stackable would be able to inherit the styles from it, to better align things with it. Our blocks would look the same, so you are free to use Stackable blocks whenever you need more design powers, or native ones for writing content.

I'd like to point out that unlike in Elementor where they create their own drag-and-drop interface on top of WordPress where you add widgets to build a page, Stackable let's you use Gutenberg fully and then Stackable adds more functionality to it, like blocks, the design library, dynamic content, etc.

We'd usually like to say that we put the "page builder" inside the block editor / Gutenberg.