My wifes Sporty had that same exact seat on it. I can't testify much for it's 2-up riding comfort...as it was her bike and only 2 or 3 times did we double up on it, only for very short rides. She loved the primary seat on it.
I've had Mustang seats on my other bikes...love 'em. The Regal Duke is my favorite...I like the pillow top seats...kinda old school chopper style. There's a wide version of the Regal too.

That touring model you linked above is quite popular and very well liked.

 

I agree with stonecat on this one.
People have been riding from coast to coast on softails for decades. They require little more than a seat upgrade to become outstanding long distance motorcycles. Don't be fooled into thinking just because there are better machines for long distance two up riding, that Softails aren't still an excellent option.

 

Go rent an RK and try one out.

 

My original plan was to ride the Sporty this summer and then decide next fall/winter if I wanted/needed to upgrade. So I would have a full season of riding under my belt and would know what type of riding I enjoyed and planned on doing going forward. If I could get her comfy enough on the sporty to find out if she really likes riding or if it would only be an occasional thing would also help me know how much consideration of 2up riding to put in the equation. Salesman I've dealt with at the local HD shop emailed me this morning that he just took a RK in on trade and he has three 2012-2015 Heritages with low miles on as well. Told me to come and ride all of them when I had time. I like Norty Flatz suggestion and rent for a day and really try them out.