I'll second your assessment of N. Citico. You should try that one in the winter. I think it has five stream crossings with one of them being very close to a waterfall. (which tends to be more challenging when frozen)
I don't think that you can go wrong here. The one thing I would NOT plan on is big miles. These aren't well groomed AT miles. I've done 12 mile day hikes with no pack weight that have taken the better part of a day.
If you're wanting to cover miles, you might consider doing the BMT section through the area. It is not easy, but it is better maintained.
The REALLY cool part about Citico/Kilmer/Slick Rock is that no permits are required and you can camp where you want. Just be sure to hang your food, and watch out for some of the 500+ lb pigs.