Posts in multiple Categories different single.php

Instead of making it category specific you could use post formats and use different content-templates. In single.php you can write

<?php get_template_part( 'content', get_post_format() ); ?>

Then create different post formats

add_theme_support( 'post-formats', array( 'withpictures', 'withcomments' ) );

Then create different post templates content-withpictures.php, content-withcomments.php

When creating content the chosen post format will determine the template.