I'm a little late to this thread but if you are interested in the Katy, you might want to check out a blog I did of my 6 day trip in September of 2018. I started at the trailhead in Clinton and headed east... I really enjoyed my time on the trail and I think my blog will give you an idea of the terrain and the trail in general. It also includes a short video of each day... I'll be 60 this year and plan on doing the GAP/C&O as my next adventure.

https://www.jimbikesthekaty.com

Jim