When does it make sense to have your solution be a web app vs a mobile app or have both?
I've tried both and it's exponentially harder to do an App vs a website. Development is slightly harder, the main downside of an app are the hurdles surrounding distribution. With a website, you click deploy and boom - the latest version is available. Need to roll back a breaking change, easy peasy. With apps, it's so much more involved and everything surrounding it just cost more of your time.
If you're doing something by yourself, avoid doing an app if possible.
That being said, apps definitely provide benefits. Being able to send push notification reliably, and being installed on someone's phone does make your service more easily accessible to the users. Also, some services don't lend themselves to being websites. For example, if you need device capabilities such as GPS, Bluetooth or storage.
Depends on your customers, solution, market strategy, etc! Often apps give you more opportunities to touch your customers and involve them
In my opinion, a mobile app only makes sense if you want to access native functions of the device that you can't use via web app. However, the boundaries are now blurring as mobile browsers offer more and more features and there are also hybrid approaches like hotwire that allow you to access native features of the phone from a web app.
And currently still basically: game development only native.
I would always prefer a web app as far as possible, since you have many advantages with it: