That's good.

You don't need to use third party extensions such as K2 or JomDirectory to get a better SEO on your website. Those extensions are meant to add extra features to Joomla core content component, but not to improve SEO, they have no difference.
About sitemap types, you should add to the robots all formats that are meaningful for your website, normally only XML and Mobile. if you have multiple languages you have to add all links, one per each language. So each sitemap will index one language.