I have a few friends who graduated from Thapar University and according to them, there is no such or major difference between COE, CAG, and CML. As well as in terms of placements and job opportunities there can be no difference found. COE includes both the software as well as the hardware aspects of a system. If you are interested in job opportunities in the gaming industry or graphics-related industry then you should definitely go for it. Your job opportunities will not be affected by your branch.
These subjects were introduced to give students options as per their interest further in COE. From the 4th semester onwards you are given the option to choose between any of the three.