Ran across this article in my news feed yesterday. I have long tried to be as paperless as possible. I have also tried to minimize apps that I need on my phone and tablets. The five categories listed in this article are a great start.
One thing I want to mention: When looking for a solution for document syncing and document scanning, you may want to consider Google Drive for both. When using Drive, you can scan a document in and save it directly to Drive from the same app, then edit it or share it out in one app. May not seem like a lot, but not having to swap back and forth from app to app.
As for the to do app, I have been using Wunderlist for more than 5 years. Great features, easy to use, and easy to share with a team.
So give the article a look see, test drive some of the apps, and if you have any others you want to share, feel free to add them in the comments box.