Confused about K2 Article App Plugin and K2 Inbuilt App

I find the EasySocial's inbuilt app and the separate K2 Article App to be confusing. I go back and forth trying to understand what does what. I already read the description in App directory for K2 Article App plugin. Out of all the features in it, the only reason I want to use that plugin is for adding stream updates when user creates new articles and for giving points and badges for K2 articles. So far so good. But when I go to EasySocial Backend settings -> Applications -> Select Type "Applications" -> User — K2, I see that this also has settings for showing stream items for K2 and also displaying list of submitted K2 Articles in profile. So my confusion is:

1) The "User — K2 settings" that I see, that is due to the inbuilt K2 Application isint it? Or is it due to me installing the K2 Article App Plugin. (I am assuming its inbuilt since it appears even when the K2 plugin is disabled).

2) Why do I need the K2 Article App Plugin when the inbuilt K2 app already has settings for adding Stream items from K2 articles? I thought only the K2 Plugin can do that (i.e adding streams on newly created articles). Have I misunderstood the purpose for App and Plugin?

3) Why cant you integrate both the K2 Article plugin and K2 inbuilt App together as 1 instead of having it as 2 separate things?