We never keep copies of files longer than needed to deliver you a speedy service. To be exact, when you use any of these features, we are storing something temporarily:
All other features do not cause any storage on our service. The goal is actually to re-use your existing storage more easily and to not compete with these services.
We are also considering adding an extra option 'Full Privacy Mode' for pro-users, which would remove these functionalities from the app. We also have an Enterprise plan, where the server-part of our app that causes storage can be deployed at the client.