Create A Loop With A Variable Number of Posts For Each Bootstrap Row?

The easy-but-a-bit-hacky way to get there would be to initialize a counter variable before your loop and then use that to tell what post you’re on. something like so:

    $paged = (get_query_var('paged')) ? absint(get_query_var('paged')) : 1;
$args = array(
    'post_type'      => 'workshop',
    'post_status'    => 'publish',
    'posts_per_page' => 11,
    'paged'          => $paged,
);
$customQuery = new WP_Query($args);
$counter = 1;
if ($customQuery->have_posts()) :
    while ($customQuery->have_posts()) : $customQuery->the_post();
        if ($counter === 1) { ?>
            <div class="row">
                <!-- ROW 1 -  FULL SCREEN WIDTH MARKUP -->

            </div><!--/.row-->
            <?php
        } elseif ($counter <= 5) {
            if ($counter === 2) { ?>
                <div class="row no-gutters">
            <?php }
            ?>
                <!-- ROW 2 - [FOUR POSTS] MARKUP HERE -->
            <?php if ($counter === 5) { ?>
                </div><!--/.row-->
            <?php }
        } else {
            if ($counter === 6) { ?>
                <div class="row no-gutters">
            <?php } ?>
                    <!-- ROW 3 - [Six Posts] Markup -->
            <?php if ($counter === 11) { ?>
                </div><!--/.row-->
            <?php } 
        };
        $counter++;
    endwhile;
endif;