How to style first post differently and wrap the others in their own container

If you are trying to style the first post with different HTML and others with other HTML structures. Then this code may help.

<div class="dpe-flexible-posts row">

<?php 

$firstQuery = new WP_Query('showposts=1');

if ( $firstQuery->have_posts() ) {
    while ( $firstQuery->have_posts() ) {
        $firstQuery->the_post();
        ?>
        <div <?php post_class('col-8'); ?>>
            <div class="dpe-flexible-posts-inner magB30">
                <div class="post-thumbnail">
                    <a href="<?php echo the_permalink(); ?>">
                        <?php
                            if ( $thumbnail == true ) {
                                // If the post has a feature image, show it
                                if ( has_post_thumbnail() ) {
                                    the_post_thumbnail( $thumbsize );
                                // Else if the post has a mime type that starts with "image/" then show the image directly.
                                } else  { ?>
                                    <div class="entry-image">
                                      <a href="<?php the_permalink(); ?>" rel="bookmark">
                                    <img src="<?php echo get_stylesheet_directory_uri() . '/inc/assets/img/default-image.png'; ?>" alt="<?php the_title(); ?>" />
                                    </a>
                                    </div>
                                <?php } ?>
                            <?php } ?>
                    </a>
                </div>
                <div class="dpe-posts-content">
                    <h3 class="h2"><a href="<?php echo the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></h3>
                </div>
            </div>
        </div>
        <?php
    }
}

$secondQuery = new WP_Query('offset=1');
if ( $secondQuery->have_posts() ) {
    while ( $secondQuery->have_posts() ) {
        $secondQuery->the_post();
        ?>
        <div <?php post_class('col-4'); ?>>
            <div class="dpe-flexible-posts-inner">
                    <div class="post-thumbnail">
                    <a href="<?php echo the_permalink(); ?>">
                        <?php
                            if ( $thumbnail == true ) {
                                // If the post has a feature image, show it
                                if ( has_post_thumbnail() ) {
                                    the_post_thumbnail( $thumbsize );
                                // Else if the post has a mime type that starts with "image/" then show the image directly.
                                } else  { ?>
                                    <div class="entry-image">
                                      <a href="<?php the_permalink(); ?>" rel="bookmark">
                                    <img src="<?php echo get_stylesheet_directory_uri() . '/inc/assets/img/default-image.png'; ?>" alt="<?php the_title(); ?>" />
                                    </a>
                                    </div>
                                <?php } ?>
                            <?php } ?>
                        </a>
                    </div>
                    <div class="dpe-posts-content">
                        <h3 class="h5"><a href="<?php echo the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></h3>
                    </div>
            </div>
        </div>
        <?php
    }
}