What is the best practice to customize any module?

- Should we update code? or should we make configurations from UI?

For example Define rules, rights, change in view of model, add some stages to workflow, change in model field and many more.

which is the best way and why?

If we make changes from UI configurations and technical features , will it work in production mode as we customize in development mode?

If it is possible then how to deploy module from development to test and test to production?