Greetings Adharsh,

This all courses you will come across doing B Tech in Mechanical.Now all this courses are related to each other you cant skip any of the subjects as its concept might help you in your industry life.
Now coming to the point, Product design, CAD,Integrated Manufacturing Design,Mechatronics all are the digitalised subjects of Mechanical Engineering. This all subjects are the recent trends in the industries.So to cop up with the industries you need to understand the basic concept and also to implement it in practical life.Masters of the above mentioned courses will help you to be Specialized on the subject and you can work as aa team man in the industries.I would suggest as per the current trends are concerned,you should choose Mechatronics as it is a budding subject and also very much interesting as well.

Good Luck!!
Regards Ankit!!