How to add parameters for custom post type

Question

You want posts_per_page but you would have to create 2 queries to pull in 4 of each tag as the default code will pull in posts from either of the tags, not an equal amount between them.

$args = array(
 'post_type' => 'customer-stories',
 'tag' => 'microsoft',
 'posts_per_page' = '4'
);
$args2 = array(
 'post_type' => 'customer-stories',
 'tag' => 'microsoft',
 'posts_per_page' = '4'
);
$query1 = new WP_Query( $args );

// The Loop
while ( $query1->have_posts() ) {
    $query1->the_post();
    echo '<li>' . get_the_title() . '</li>';
}
wp_reset_postdata();

$query2 = new WP_Query( $args2 );
while ( $query2->have_posts() ) {
    $query2->the_post();
    echo '<li>' . get_the_title( $query2->post->ID ) . '</li>';
}

That should get you most of the way to a solution