Big Bend NP on the Rio Grande would be one of my top picks. A beautiful park with hot springs, a waterfall, and an awesome canyon. People flock here in the spring to see the cacti in bloom. But folks don’t realize that in this arid area cacti also bloom in the fall. It is lovely rugged, unique, and uncrowded in the fall.
What are you interested in doing or seeing? Consider exploring the Upper Peninsula of Michigan if you like hiking, waterfalls, forest camping, awesome views of Lake Superior, etc. Just note that cellular service can be almost non-existent between towns.