You can use any query parameter from WP_Query: https://codex.wordpress.org/Class_Reference/WP_Query if you want to change the post per page you can also use this filter: buddyforms_user_posts_query_args_posts_per_page

buddyforms_user_posts_query_args.php

<?php
/*
 *  Manipulate the user posts list query
 */
add_filter( 'buddyforms_user_posts_query_args', 'my_buddyforms_user_posts_query_args', 10, 1 );
function my_buddyforms_user_posts_query_args( $query_args ){
	global $buddyforms;

	$query_args['cat'] = '4';

	return $query_args;
}