WP custom posts: filter results to custom taxonomy tag that corresponds to user meta field

You would not do this using SQL, and you don’t need to. Use PHP instead.

For example, this code adds a search parameter to the query, but the value changes depending if the user is logged in:

add_action( 'elementor/query/article_video_together', function( \WP_Query $query ) {
    $foo = is_user_logged_in();
    if ( true === $foo ) {
        $query->set( 's', 'logged in search term' );
    } else {
        $query->set( 's', 'logged out search term' );
    }
    $query->set( 'post_type', [ 'article', 'video' ] );
} );

You can do the same using get_user_meta and the post tag parameters of WP_Query.

Note that this answer was written assuming that elementor/query/article_video_together works the same was as the pre_get_posts action. If it does not, then you need to go to Elementor support or ask in an Elementor community