I have Nextcloud configured with a versioned and encrypted S3 bucket as the data store so everything’s “private”, constantly backed, up and synced.
I use one line for one task. If I need to write subtasks or some points I use tabs under that task. For different days I use visual separators like ---- or ===.
Example:
===Today===
First task
Second task
More info about task
Subtasks 1
Subtasks 2
===Tommorow===First task
Second task
The text files contain both notes and to-dos.
I like that this setting feels that my notes will live forever.