Is there a smart way to obtain a list of only some selected user meta data?

I think you should stick to WP_User_Query. There you can simply specify the fields you want to use to select certain users. Also meta fields.

WP_User_Query is a class, defined in wp-includes/user.php, that allows querying WordPress database tables wp_users and wp_usermeta.

But yes(!), this will not return you user meta values. Even when setting 'fields' => 'all_with_meta'.

all_with_meta currently returns the same fields as all which does not include user fields stored in wp_usermeta. You must create a second query to get the user meta fields by ID or use the __get PHP magic method to get the values of these fields.

That said, my conclusion would be to indeed use meta_query in a WP_User_Query to select users by certain meta values and use that result to retrieve additional meta data by calling for example get_user_meta($user->ID, 'meta_key', TRUE).

$user_query = new WP_User_Query([
  'role'       => 'editor', 
  'meta_query' => [
    [
      'key'     => 'meta_key',
      'compare' => 'EXISTS', // Use 'NOT EXISTS' for non-existance of this key.
    ],
  ],
]);

$editors = $user_query->get_results();

foreach ($editors as $editor) {
  $first_name = $editor->display_name;
  $meta_value = get_user_meta($editor->ID, 'meta_key', TRUE);
  // ...
}

That’s one hundred times more readable and maintainable than a custom database query, in my opinion.

And regarding performance, maybe check out this related answer on the same topic just for post meta data: Can WP_Query return post meta in a single request? which links you to: Custom post meta field effect on the performance on the post.

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