Hi,
1. This does not change the URL of the results, it only changes where the user is redirected when clicking on the magnifier icon or hitting the enter key. The only way to change the result URLs is by using a custom code. You can read about it in this knowledge base tutorial.
The default value of that option is:
?s={phrase}
2. Do you mean how to search posts and pages (and other custom post types) by categories or tags? By enabling this option: https://documentation.ajaxsearchpro.com/general-settings/search-in-terms-categories-tags…