The Tiles layout is a flexible jQuery masonry layout that renders K2 items in a fluid grid, based on a vertical alignment. Each item's position is organised based on the availability of spots vertically as opposed to a more traditional grid which organises elements horizontally. It's like a jigsaw for your K2 content.
Zenkit contains two layouts based on what is best called a magazine layout. The magazine layout contains a larger leading column of items with a smaller column which contains the primary group of items.
The Zenkit accordion layout is unique in that it does not have it's own template but is rather a styling that can be applied to other layouts. The accordion mode is triggered via the use of a page class suffix and does not have a separate accordion file like the other layouts.
Zenkit styling is minimal because it was built with the idea that your template should fill in the gaps of how it should look. There is some styling information built into Zenkit but on the whole it relies on your template to make the decision on how specific elements should be styled.