No now you can’t change. Only after the counseling is done you can approach them regarding change of campus but that too now you have to take branch in category 4 if seats are available. You can’t change after you have booked your place in particular campus.
From my point of view there isn’t any difference between VIT Vellore and VIT Chennai it’s just the campus is big rest all are same.
Considering the placements Chennai students have to go to Vellore for placements or vice versa depends on the company where they want to continue there process in last year of graduation.
I was in VIT Chennai Mechanical branch then also I got placed in Tolaram group which offered me 23lakhs (highest in university in mechanical) P.a. Total 3 student got placed other two were from Vellore.
So it’s just Chennai students have to go and attend the process at Vellore which is just 2:30 hrs away from Chennai Campus.
So just don’t go for placements both the campus have common placement procedure whereas it also depends on your interest.