While all layouts are using the same content elements,  they are making use of media assets differently. For example - when using a horizontal image or video - it’s better the avoid using a full-bleed layout, that’s likely to discard the content on the sides.

How to access: Story Editor > Layouts and Presets tab on the right side
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Layouts do not carry colours or fonts presets. To create such presets - please use the Skins tab in the Layouts and Presets section.
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Tip: Alternating layouts across your story will keep your users engaged for longer and will make your story more exciting to explore.