with the example above you’d need 2 sidebar files
sidebar-first-sidebar.php
sidebar-second-sidebar.php
and like your original sidebar.php you add
<?php if ( !function_exists(‘dynamic_sidebar’) || !dynamic_sidebar(‘first-sidebar’) ) : ?>
<?php endif; ?>
and
<?php if ( !function_exists(‘dynamic_sidebar’) || !dynamic_sidebar(‘second-sidebar’) ) : ?>
<?php endif; ?>
For the style it’s what you put in the before_widget
.right-widget and .left-widget