I have custom requirement to do , what is the best way to do it?
develop it as a plugin or customize source code (core).
The best way is to customize nopcommerce using plugins. You can override part of the code, add extension, custom logic by using plugin. But It will be time consuming and costly sometime. If you have those issue you can customize the code directly. but plugin is the best way to customize nopcommerce.
If you need to know more details, please ask me your questions.