Born and raised in Memphis; family still there. Walkability + safety is limited to a few areas in downtown (Harbortown/Mud Island), Midtown, and Collierville (historic part).
If biking distance or short car ride is okay, your options expand quite a bit: all of Germantown, most of East Memphis, and the rest of Collierville.
Hiking: Wolf River area, Shelby Farms, Meeman Shelby Park, TO Fuller State Park