Yes, you can create and manage multiple apps! Each app will be billed separately and you can choose a different pricing plan for each app. When you are ready, just hover over the app 'switcher' in your dashboard on the upper lefthand side of the menu (near your app icon) and hit the "Create App" button, you'll then be prompted to fill out a new app form.
Each app runs as a completely separate entity in that it has its own users, styling, domain and settings - but you are able to create libraries of content that can be shared between the apps. You can switch between apps from your account by hovering over the switcher in the left-hand navbar.