I will restrict my answer to Engineering Physics and Chemicals only as I know the same only. 

• The major criterion followed at IIT Delhi by all the branches is a well-maintained CG. To secure good placements one has to constantly score a good CG throughout the program.
• During your admission, the department does not play any role but your 85 percent constraint on minimum possible strength does.
• Engineering Physics is a unique branch for those highly passionate about Physics and want to pursue higher studies in the same
• To secure core jobs, one has to move to MTech in Engineering Physics from BTech in Engineering Physics.
• For Chemical Engineering students, BTech is more than enough to secure decent packages and great research opportunities outside India.
• Consultancy and Analytics jobs are offered equally to students of all the departments 
• Engineering Physics graduates usually take up consultancy or IT jobs 
• Chemical Engineering is the most laid-back department of IIT Delhi with very flexible academics thus making it easy to maintain a decent CG throughout. 

I wouldn’t suggest anyone go for Engineering Physics if they have no intention of pursuing it later. Instead, look for other options in BTech and explore your interests.