Upward mountains were formed into layers by an igneus or sedimentary process they will more likely look rounded I think. If they were formed by uplift during a collision of techtonic plates, they were literally shoved upward. Depending on the material they are made from, they will erode at different rates. So a crumbly rock may continue to break off in chunks over time leaving a jagged, rough appearance. A smooth hard rock will not break off so easily since water cannot get into cracks and freeze, expand, and push chunks out to fall off.