Yes, you have the right idea.
When you are describing physical characteristics, narrow and wide refer to the space between two sides of something. For example, you describe a road, a path, a corridor or a river as narrow or wide. Your examples about objects that are thick and thin are also correct.
You can also describe a person as thin, if they have a very little body fat. However, the opposite of 'a thin person' is 'a fat person'. You can also use other terms such as overweight, plump, chubby, stocky, well-built, solidly built, but not 'thick'.