The 2N or 2T as it's also called is just the command rate. It's listed for one set of RAM and not listed on the other.
The Ripjaws is an older model than the Ripjaws X. Most likely since all the other specs are the same they put new heat spreaders on it and gave it a new name but it's the same RAM modules. The Ripjaws X may have newer XMP profiles as well.