For hosting common files it's ok. Also it is on Android too do, great to transfer files between your Windows and your phone. But if you want better security you have to subscribe a monthly offer.
I guess it's really safe cause it's open source, you can make notes on your habits but don't really do that. Its simple. Really fast. Haven't found a way to connect it to notion. In general it's a great app to track you habits. Does its job. Not more, not less.
Dropbox - Online Sync and File Sharing
Habitica - Habitica is a free habit building and productivity application.
Google Drive - Access and sync your files anywhere
HabitBull - HabitBull
Mega - Secure File Storage and collaboration
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.