If you wish to get seat in main campus and in top branches like CS then you will have to score 100+ as this would be safest score to get seat there but this is a tentative score as VIT only declare the ranks. Also, if you talk about difficulty level then Jee mains is more of in depth knowledge of each topics so if you are able to crack Jee main easily then chances of getting decent rank in VIT is possible and the plus of VITEEE is there is no negative marking. So it is advisable to prepare very well for Jee so that you can easily crack exams like VIT, SRM, Manipal etc as the syllabus of them is almost the same.

Good Luck!!!