@angular2, @angular2-components, @angular2-modules
What would be better approach whether to create child modules of app module or different components for different features of project using angular2
from design and business perspective ?
ng modules simply logical units that contained components, services, pipes, directives, providers, etc.
The main benefit of ng modules is that they help you to organize the logical structure of your app - this way is much easier to maintain the codebase over time, etc.
There is a different types of modules:
A while ago I was giving a talk on that matter also you might take a look at code sample
Also I would recommend to watch this talk https://www.youtube.com/watch?v=ntJ-P-Cvo7o from the latest ngconf that covers the purpose of ng modules.