Obsidian stores notes on your device, so you can access them quickly, even offline. No one else can read them, not even us. With hundreds of plugins and themes, you can shape Obsidian to fit your way of thinking. Obsidian uses open, non-proprietary files, so you're never locked in, and can preserve your data for the long term.
Todoist is consistently one of our favorite to-do apps. The company is pretty good about releasing useful updates, and today it's adding a Boards feature that should make it even easier to organize and visualize your tasks and projects. The Boards format makes Todoist look a whole lot like Trello, another one of our favorite project management apps. The feature lets you view tasks as cards, and you can drag the cards horizontally into customizable categories. If you're not totally sold on the format, you can switch projects back and forth between cards and traditional lists as you work.