Less techy than what you mentioned, but why not throw some bags on your bike and ride the
GAP? Regardless of which way you go - DC to Pitt or Pitt to DC, you can catch the Amtrak with roll-on service to get back. I did this ride back in '17 in basically 48 hours - started Sunday afternoon and finished on Tuesday afternoon - so it's more than doable in four days. And I'd actually recommend taking more time than I did because there are some pretty cool towns you can stop in along the way (Harper's Ferry, Cumberland, Ohiopyle just to name a few.) I'd check to make sure camping is available that late in the year, but even if there isn't, there are plenty of places to stay along the way - just have a daily mileage plan if that's what you're going to do: some of the more remote towns (e.g., Confluence) have accomodations but the towns themselves tend to close down after dark and it becomes tougher to get food, etc. (Learned that one the hard way after day 2.) Knowing where you plan to stop ahead of time removes that problem. Anyway, it's not a technical ride by any stretch, but it is long, remote in spots, and really beautiful (especially the actual Allegheny section in PA.) Some logistics: I parked my car in DC at Reagan Int'l and I'd strongly recommend doing this if you start in DC. Where I parked, I was basically right on the Mount Vernon Trail that goes from Alexandria into Georgetown, right where the C&O starts. I didn't plan that, it just worked out nicely and you can use the monuments to easily get back to it from the train station when you get back to DC - you can basically see the Mount Vernon Trail from the Washington Monument facing away from the Grand Mall. And on the other end, in Pittsburgh, the trail ends at the same fountain that serves as the Pittsburgh terminus for the CtC ride every April, so it's convenient to multiple hotels right in the downtown area - I stayed in one that was a stone's throw from the train station. The train leaves kind of early - I think you board at 5:30 am (at least you did in '17) so it was very handy to be that close. And after riding 350 miles, cruising back along the same route on a train is a nice, relaxing way to experience the scenery a different way. Honestly, I've done vacation bike trips all over the country at this point and I have to say this one is probably one of my most memorable.