ACF works more simply than other “page builders”. ACF is not really a page builder. ACF works by sending all of the data in $_POST in a single request. Other systems use AJAX to update data as you work, ACF does not. ACF is built on the idea of using only what core WP offers for managing custom fields. It does not do anything that you could not do by creating and managing your own custom fields with your own processing using WP add_meta_box().
I routinely set max_input_vars to 10,000 or even higher on ACF heavy sites. But 10,000 is my general starting point when I’m building a custom site using ACF.
This plugin has not been updated in a long time, but it still work, and give a warning when the inputs on a page exceed max_input_vars https://wordpress.org/plugins/wp-max-submit-protect/
