If you haven't tried, after you use Cmd-Ctrl-F to make Chrome fullscreen you can use Cmd-Shift-F to toggle the UI elements (tabs, search bar & bookmark bar). Although it doesn't follow your mouse hover which is somehow annoying.
Cmd+s in Arc just hides all the UI of the browser but does not change the size of the window frame. This is more akin to Chrome's add shortcut to desktop feature, except that it is easy to toggle on/off with a keyboard shortcut. So if you have a web app you want to just focus on, you can just do so.