The difference is that jeans with small feet are getting thinner from calf to ankle. Narrow-leg jeans are slim only at the trouser legs.

Jeans with small feet are tapered pants, also called pencil pants. Legs are as thin as ankles, and the whole pants are tapered pencil pants, which originated from British pencil pants and are often called drain jeans and cigarette pants. They are a kind of tight jeans, also called narrow trousers. Figure 1: jeans with small feet.

Narrow leg jeans are a kind of small leg jeans. Figure 2: Narrow leg jeans.