I can’t provide much guidance with your route, but I can offer some thoughts on driving a 26-foot moving truck—having just made a 1,000-mile move with one earlier this year.
First, have you already made a rental reservation for your truck? I’d definitely recommend against renting from U-Haul for a few reasons. To keep it short: aging, poorly maintained equipment; anemic gas-powered trucks; flaky “reservations” system. Do some searches along the lines of “uhaul maintenance lawsuit”, “uhaul complaints” and you’ll get an idea. Additionally, I’ve never found Uhaul’s prices to be competitive for long distances when fees and fuel costs are taken into account.
In terms of equipment and customer service, I’ve had much better experiences with Penske, Budget, and Enterprise. And particularly for a truck as large as 26 feet, I’d absolutely recommend renting a diesel-powered one.
As long as you keep to Interstates and other major routes with moderate grades, I wouldn’t worry too much about hills or road geometry. Earlier this year, I drove some long, steep grades on I-77 and I-81 with a 26-foot diesel-powered International loaded to within a few hundred pounds of its 26,000 lb. rating. And I was able to at least keep pace with the tractor trailers climbing those same grades.
Of course you have to remember that you’re not driving a car: Keep to the posted speed limit at a maximum, abide all advisory speeds, use a lower gear on steep downgrades, keep in the right lane even if it means going a bit slower than you’d prefer, etc. Patience will be perhaps your greatest asset.
I would stick to service facilities and hotels that are designed to accommodate large trucks and avoid having to back up or make any tight maneuvers. That should be fairly easy to do on any major route, but a look at some of the major truck stop chains (TA/Petro, Pilot/Flying J, Love’s) location finder tools might be a good resource to help plan the best route.
Good luck!