There's no mystery about Quay - if you know how to follow an alias to the original file (Command-r), a feature of the Mac OS since at least OS 7.5 - you'll find the Quay app and its associated files in the user folder>Library>Applications Support>Quay.quay file. Right click on the file and select Show Package Contents. You can do the same to the oddly named files inside to see the default Quay icons for the Applications and Utilities folders and any custom folder icons you design in Quay. As to whether you need the functionality Quay provides, that's a matter of individual preference. Quay has become less essential as the Dock has improved though Quay, too, has improved along the way.