Hi guys,
How can I disable the RSS feed/blog generation completely. I don't want this content or urls generated.
We're not using this and it's cluttering the overview of our content, for instance when I'm entering the SEO data.

Thanks a lot for any helpful advice!

You can disable the link and the rss icons from your category settings. The menu item also has similar settings so make sure you edit that as well.

Does the deleting/disabling of the icons also prevent the generation of the content?
When I create a menu item of one K2 category I cannot disable the icons again because they're greyed out and use the settings of the category.

Because the content is there SH404SEF creates url's and this makes it more difficult to manage the url's that I DO need.

Actually these links will not affect your SEO in any way. Feeds will also benefit SEO.
Turning the entire site's feed is something you cannot do. ?format=feed is generated globally from Joomla!.

The settings are located in each category. These options on the menu item become available if you select multiple categories.