Do I need a mobile app or website?

The difference that has the most consequences is distribution. A website is a URL — you ship a fix and everyone has it on their next load, and search engines can find you. An app has to be installed, updates go through review, and a share of your users will stay on an old version for months, which means the API behind it has to keep supporting what you shipped last year.

So the question is whether anything about the product actually requires being installed. If it does not, a well-built responsive site — optionally installable as a progressive web app — reaches more people for less, and gives you a real audience to test an app against later. The expensive version of this decision is building an app first and discovering the hard part was never the platform.