It might surprise you but I find that the Fujifilm 50mm F2 WR lens is my most versatile lens when I walk with my X-Pro2 camera.  I like that prime lens since it is the best compromise in weight, size, weather resistance, close focusing, and focal length versatility when I go walking.  I can use it inside along with cropping in poor light situations as well as outdoors with cropping.  You might be thinking that a zoom lens would be more versatile but they are larger and heavier and I mostly use them when I’m fixed in a small area and I don’t need to carry them while walking over longer distances.  I actually prefer to carry only one small pancake lens on my X-Pro2 but they are more limited in focal length capabilities.  I sometimes use the X-Pro2 with one prime lens along with the X-H1 and another prime lens when I’m photographing an event while walking in narrow halls.