The first thing I would do is simplify the code. You don’t need all those if/elseif statements and you can reduce the number of post loops to 1 using the values from the sub fields.
But you will need to build a card template part for the case studies
<?php
if (have_rows('row_order_and_qty')) {
while(have_rows('row_order_and_qty')) {
the_row();
$post_type = get_sub_field('content_type');
$posts_per_page = get_sub_field('items_per_row');
$row_query = new WP_Query(array(
'post_type' => $post_type,
'post_status' => 'publish',
'posts_per_page' => $posts_per_page,
'orderby' => 'date',
'order' => 'DESC'
));
if ($row_query->have_posts()) {
switch($post_type) {
case 'auction':
$icon = '<i class="fas fa-gavel"></i>';
$heading = 'Auctions';
$class = 'row row-cols-1 row-cols-sm-1 row-cols-md-2 row-cols-lg-4 row-cols-xl-4';
$link_url = '/auctions';
break;
case 'liquidation':
$icon = '<i class="fas fa-file-invoice-dollar"></i>';
$heading = 'Liquidations';
$class = 'row row-cols-1 row-cols-sm-1 row-cols-md-2 row-cols-lg-4 row-cols-xl-4';
$link_url = '/past-auctions';
break;
case 'inventory':
$icon = '<i class="fas fa-award">';
$heading = 'Featured Inventory';
$class = 'row row-cols-1 row-cols-sm-1 row-cols-md-2 row-cols-lg-4 row-cols-xl-4';
$link_url = '/inventory';
break;
case 'studies':
$icon = '<i class="fas fa-file-invoice"></i>';
$heading = 'Case Studies';
$class = 'row row-cols-1 row-cols-md-2 row-cols-lg-3';
$link_url = '/studies';
break;
} // end switch
?>
<h2 class="section-title mt-5"><?php
echo $icon; ?> <?php
echo $heading; ?>
<a href="<?php
echo $link_url; ?>" class="font-weight-normal text-right badge badge-primary">View All</a></h2>
<div class="<?php echo $class; ?>">
<?php
while ($row_query->have_posts()) {
$row_query->the_post();
?>
<div class="col mb-4">
<?php get_template_part('template-parts/card', $type); ?>
</div>
<?php
} // end while have posts
wp_reset_postdata();
?>
</div>
<?php
} // end if have posts
} // end while have rows
} // end if have rows
?>
