You only need to worry about devDependencies vs dependencies if you are going to publish the project you are working on as an npm package. If you are making a webapp or something else that you will run, then it doesn't matter.

I find postman to be too complex, too much config all over the place. It's also difficult to share with others, it would be much better if it could store the settings in a file that could then be checked into git. That way everyone on the project would have the requests and could add and modify them as the server changes. Does any client like this exist?