One giant app with multiple modules or multiple apps

One giant app with multiple modules or multiple apps

Hello, in planning for developing creator apps for several aspects of my business (inventory, hr, and billing to start) would it be best practice to make one big app that includes these different pieces or make multiple apps because the uses are too different?

What should be the main factor for considering one method or the other?

Another question I had if I go multiple app route: if app1 is not shared with a user but app2 is shared and if app2 had lookup fields from app1, would the user be able to see the lookup fields from app1?