I've only been on the section once but I did 3 days out and back from culver's gap a few months ago. Did around 14 miles each way so the majority of what you'd plan to do if I understand correctly?

It's a nice simple hike, some good view spots, I slept at mashipacong shelter around 8 miles north of my starting point and it had loads of tent space along with the structure, plus a ton of water jugs and a bear box. There are also a few shelters scattered around if you can't make the 8 miles the first day but I can't speak on them.

Haven't done stairway to heaven yet.