Three thumbnails per row was pretty tight for most phones since the most common phone resolution is 360x640. Two thumbnails per row lets us have thumbnails up to 180x180 in size.
Components
Components are used to encapsulate common UI widgets used throughout the site. This includes things like comments, tag lists, post thumbnails, paginators, and other things used repeatedly throughout the site. Components encapsulate a widget's HTML, CSS, and Javascript together so that all the code for a component is in a single place.
This uses the ViewComponent library.
Components are similar in concept to React components.