Dear aspirant,

The syllabus for all the engineering entrance exams are almost the same. The questions for JEE Mains are slightly harder than that of the VIT and SRM. So, you would definitely cover the syllabus depth for these exams while preparing for JEE Mains. You might have to practice to finish the questions faster for VIT and SRM. So, if you can practice chapter wise mock test every month for your exam of interest, the concepts and practice you have had for JEE Mains will be more than enough. Make sure that you take time out to solve previous year question for SRMJEE and VITEEE.

Hope this helps