So I've been fighting with the Project app from the start and I seem to already have a better solution for my needs by building my own app. 

The big concern is whether or not I can use the Planning app with this custom project management app I'm building. Can anyone advise?

Some of my problems with the Project app is we need to be able to click on a project and see an overview of the project, with chatter, and then you can click in to tasks.