Here are my answers ,
1 . When you use blog plugin , it create a separate URL for all blog functionality . When you access http://blogdemo.q2a-store.com/ask
this will create normal questions . If you want to create posts then you need to navigate to http://blogdemo.q2a-store.com/blog/new
2. You have all flexibility to change the base blog URL something like - notes , pages , posts (What ever you want ) . So at that time you need to access new post page like this http://blogdemo.q2a-store.com/note/new
3. It is a completely separate system having separate tags and categories . You can set the Categories from Admin Panel . You can also have flexibility like creating sub-categories upto 4 levels , delete category and assign posts to another categories , assign unassigned posts to a specific categories and many more .
Hope you will like the features .