Регистрация внутри регистрации через фронтенд

Создаете собственную таксономию

/* add custom post types */
add_post_type('profiles', 'Анкеты', array(
	'supports'   => array( 'title', 'editor', 'thumbnail', 'comments' ),
	'taxonomies' => array( 'post_tag' )
));
add_post_type('persons', 'Частные лица', array(
	'supports'   => array( 'title', 'editor', 'thumbnail' ),
	'taxonomies' => array( 'post_tag' ),
	'menu_icon' => 'dashicons-businessman'
));
add_post_type('agencies', 'Организации', array(
	'supports'   => array( 'title', 'editor', 'thumbnail' ),
	'taxonomies' => array( 'post_tag' ),
	'menu_icon' => 'dashicons-groups'
));
function add_post_type($name, $label, $args = array()) {
	add_action('init', function() use($name, $label, $args) {
		$upper = ucwords($name);
		$name = strtolower(str_replace(' ', '_', $name));

		$args = array_merge(
			array(
				'public' => true,
				'label' => "$label",
				'publicly_queryable' => true,
				'show_ui' => true,
				'query_var' => true,
				'capability_type' => 'post',
				'has_archive' => true,
				'labels' => array('add_new_item' => 'Добавить'),
				'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' ),
				'taxonomies' => array('post_tag', 'category'),
				'show_in_rest' => true,
				'menu_position' => 10,
				'menu_icon' => 'dashicons-clipboard'
			),
			$args
		);
		register_post_type($name, $args);
	});
}

это пример, далеев functions.php добавляете хук на регистрацию юзверга

/* After registration create user's post */
add_action( 'user_register', 'save_tml_registration_form_fields' );
function save_tml_registration_form_fields( $user_id ) {

	$post_id = wp_insert_post(  wp_slash( array(
		'post_status'   => 'publish',
		'post_type'     => 'persons',
		'post_author'   => $user_id,
		'post_name'     => $_POST['user_login'],
		'post_title'    => $_POST['user_login'],
		'post_content'  => '',// 'Здесь ваше описание о себе.'
		'ping_status'   => get_option( 'default_ping_status' ),
		'post_parent'   => 0,
		'menu_order'    => 0,
		'to_ping'       => '',
		'pinged'        => '',
		'post_password' => '',
		'post_excerpt'  => '',
	) ) );

	/*update_user_meta( $user_id, 'post_id', $post_id );

	update_field( 'user-id', $user_id, $post_id );

	set_acf_default_values( [
		'user-balance',
		'user-tariff',
		'tariff-free',
		'tariff-vip-1',
		'tariff-vip-2',
		'tariff-vip-3'
	], $post_id );*/

}