Short answer
Uptown is walkable for many museums, hotels, stadiums and arenas. South End is walkable along the Rail Trail and is connected to Uptown by light rail. A car or rideshare is useful for many outer attractions and neighborhoods.
Detailed explanation
A visitor can plan a satisfying low-car trip by staying in Uptown or near the Blue Line. However, the Whitewater Center, Carowinds, Lake Norman and numerous restaurants and family attractions are not naturally part of a single walking network.
Best strategy
Use walking and rail for central days, then use a rental car or rideshare for one or two outer-area days. Check weather and event closures before relying on a long walk.