Crossed on US-60 several times, once with RV. The roads and bridges are narrow, compared to more moden highways, but still wide enough for the heavy truck traffic that uses the route. Much of the route with minimal shoulder width, bar ditches close to the road. There are a few small towns to work your way through, but if the big trucks can handle it, RV driver should be able.
For Springfield to Nashville, I prefer US-60 to Sikeston, I-55 down to I-155, then from Dyersburd US-412 to join I-70 near Jackson. The road is better, moves faster, tha US-60 in Kentucky. I use 60 through Kentucky if going to Land Between the Lakes from Springfield, or to follow it further northeast, e.g. to Evansville. It is not the best route for Nashville as a destination, but good for places north on I-24 like Fort Campbell or Clarksville.