Post Count: How many posts you have written.
Reputation: Also known as like count. It shows how many times someone pressed the "Like this" button on one of your posts.
I am not sure about the Label but I think it was related to the post count. And it doesn't really say anything. I think everyone over 100 posts is a Well-Known-Minion. Best look at the post and like count. (Yes, I know, that's better for me But it also is saying more than the label.)
The new editor is a so called WYSIWYG Editor. Aka What You See Is What You Get. Just like Microsoft Word or LibreOffice Writer. There is no BB Code anymore because of that. It is not needed anymore. If you want to read more about WYSIWYG Editors click here. (sorry for the short answer, it's way too hot here and my brain isn't really working... I can provide a more detailed explanation if needed.)