Features / Usability

Ahhh.... you simply want to change the number of items per page.... use the Pagination Links options. Please see the docs for details.

I don't think there's an option for this, but you can easily remove the category tree by modifying the theme CSS or template TPL file. My primer provides hints on how to do this here and here.

Of course, your site visitors will no longer be able to navigate to view items in different categories. An alternative could be to use a deeper category structure (for example, create a parent "Rap" category and move all the Rap-categories to it). This way, you could toggle (show/hide) them and save screen space.