Per emailed question, utilizing the example in my blog post "User Dropdown List & Custom Notification Routing in Gravity Forms" for multiple fields that have the custom 'user-emails' CSS class to email multiple people

custom-route-notification-multiple-fields.php

<?php
/**
 * Change the sent to email address in the notification
 *
 * @author Joshua David Nelson, [email protected]
 **/
// Route to user address from drop down list, update the '1' to the ID of your form
add_filter( 'gform_notification_1', 'route_user_email_notification', 10, 3 );
function route_user_email_notification( $notification, $form , $entry ) {
    
	// Create an array to store email addresses for notification
	$emails = array();
	
	// Go through each field to find the user-emails fields
	foreach( $form['fields'] as &$field ) {

		// Make sure this is the right field
		if( $field['type'] != 'select' || strpos($field['cssClass'], 'user-emails') === false )
			continue;

		// Pull out the user id selected, by the field id and the $entry element
		$field_id = (string) $field['id'];
		$user_id = $entry[ $field_id ];
		
		// set the email address to send the email to
		if( !empty( $user_id ) ) {
			$email_address = get_the_author_meta( 'user_email', $user_id );
			
			// Just double checking the author meta is an email address
			if( is_email( $email_address ) ) {
				$emails[] = $email_address;
			}
		}

	}
	
	// If we have some emails in our array, turn it into a comma-separated list and update the notification
	if ( ! empty( $emails ) ) {
		$email_to = implode(', ', $emails );
		$notification[ 'to' ] = $email_to;
	}
	
	return $notification;
}