There are several possibilities. But you could export your app1 and call this one app2 and then throw away everything that you don't need in app2. Otherwise you could create app2 and import modules/microflows/forms. You can easily export mendix artifacts by right clicking and exporting them. It's easier to export a whole module, because you will get all the associated artifacts.
Edit after comment:
The changes will not be reflected in the app2 after a export/import. The only way to do what you want is to use the same model for both applications. But that means that app2 has more features than needed. Other ways you need to set up your app in a generic way and make all the features configurable.
Edit after second comment:
When you use the same model for two applications, App2 would have more features than needed. You could set these features up in a generic way by adding booleans to enable a feature. In each application you need some setting entity to enable/disable certain feature which you could set at runtime.
You need to make a feature only available if the boolean is set to true. So basically you need some dashboard where you could navigate to all the application features. By setting the booleans you can easily make features visible with conditional formatting. When you need more explanation, please let me know.