How to display posts from specific categories differently?

Hi,

on my website there are articles and recipes, both use the standard post format. The recipes are all in the “recipe” category and they are also sorted into specific sub-categories.
In my menu there is a link to the recipe subcategories.

On my main/front page all articles are displayed in one column with an image (thumbnail) on the left and the excerpt on the right and the title on top – more or less the standard way.

What I would like to achieve: If you click on one of the recipe subcategories, all the posts will be displayed in two columns with just the article thumbnail and the title.

How would I approach that? I can code some php and css, I am using a self-written Twentytwelve-child theme. Right now I just have no idea where to look for the necessary information to achieve this goal.

Please note: I do not want to display my categories in two columns but the posts on a category archive.

Thanks