Is the camera bag one shoulder or two shoulders?

Whether the camera bag has one shoulder or one shoulder depends on your photography purpose. If it's just a street view, simple portraits, scenery, etc. And there are not many photographic equipment to carry, so it is enough to buy one shoulder.

If you climb mountains and wade in water and take pictures in dangerous geographical conditions, you have to buy a backpack, which is more convenient to carry. Because of the balanced stress on the shoulders, you can carry more photographic equipment or other materials within your physical strength, and you can also free your hands, which is conducive to chopping obstacles with a knife during climbing.