V6 app context in modules - dealing with global methods

I do have a module with global helper methods. Stuff like api handling or global app notifications. how do I access the app context within a module? At the moment I pass related objects like app / router / $f7… as parameter when I call those methods. I wonder if there is a better, more recommended way to deal with it.

In general - what is the best practice to work with global methods? Add them as a module and import on demand on component page level? Add it to app.js, store.js oder even to app.f7.html? And how to call global methods?