I would use a task manager for stuff like this - They are already built to be able to do all of this.
As much as it would be lovely to have Agenda cover absolutely all basis, I can imagine it becoming bloated.
There is nothing worse than what should be a relatively simple application (a notes app), become cumbersome and slow with an ambundence of features.
I’d recommend things 3 for what you are wanting - This would fit the bill nicely!