In short, you should build your app's architecture around can.Component(s).
<my-app>
<some-widget></some-widget>
<another-widget></another-widget>
</my-app>
You may handle routing using a component's events. Add models when you need interaction with server, can.construct maybe usefull to keep in one place simple functionality or data that is not needed to be observable.
If you use can.component forget about EJS, only mustache templates are supported.