One downside to a Git repo is that it doesn't have an easy-to-use mobile app like Google Keep or Apple Notes.
To me the the most important thing about note taking is clicking a button and immediately being able to write something, either pc or phone. I use google keep because it's the most straight forward way for me and it is synced. I would love a replacement (because it's so limited, and don't like the desktop client...), but it needs to be as convenient.
Todo = plain text. sublime/keep/applenotes/pen+paper/whiteboard/
Work notes = outlook drafts.
Personal notes = google docs.
Some plain text conventions I use.
[ ] a todo
[x] done task. I delete it after couple weeks.
[ ] another task __some extra notes. Anything with double underscores means WIP. I just search for it and continue from there