Why does everybody and their dog think that competing with the thing that comes with all my devices for free (Apple Notes, Google Keep) is a great business opportunity? I can’t seem to wrap my mind around this.
I think its a mix of both with a lean towards A personally. Knowledge workers are increasing YoY and nearly all of them take notes. The market is huge, and its quite normal for new(ish) markets to see a large number of competitors before the winners take over and the other 90% die off. To your other question -- Google Keep / Apple Notes are good for rudimentary use cases or small numbers of notes, but otherwise don't really compare to the popular note taking apps that have popped up lately.
I'm not so good at ballparking operational expenses, but Supernotes 2 probably needs somewhere around 2000 users to break even, which probably isn't hard to achieve.
After that, the founders are fully supported to pursue their passion. Sounds like a great business model for someone who wants to do this, and I think this is why you see a profusion of utility apps with ~$10/mo pricing models on the market today.
For example I schedule tweets through markdown files https://github.com/reidjs/markdown-tweet-scheduler