Wrap every 2 posts

You need to start Row class after every 2N+1 post.

And end the Row class after every 2N+2 Post.

Try this one

<?php $counter++;
if ($counter % 2 == 1) : ?>
<?php echo '<div class="post-wrapper">'; ?>
<?php endif; ?>

<?php get_template_part( 'templates/blog/blog-2-cols', get_post_format() );?>

<?php $counter++;
if ($counter % 2 == 0) : ?>
<?php echo '</div">'; ?>
<?php endif; ?>