WP ajax VS wp-load

Hello,
I need to use some WordPress functions inside of some .php files (custom queries) outside of WordPress environment (but in the same folder/domain).
In this files I will need to use do_shortcode() and add_filter() functions.

When I use WP Ajax am I able to use those functions or I would need to include them too? (“Am I inside the WordPress environment or outside?”)
For example, would I need to do:
include “../../../wp-loader.php”;

Thank you very much!