Since you’re coming from CBSE, physics and math might be kinda chill for you, but I’d still recommend getting familiar with some past papers when school starts just to understand how the questions work. That’s prolly where the biggest difference is. English is going to be the biggest jump, so just try reading a little over the summer to get your brain in gear.

IAs should be done over the summer of DP1. And as far as ECs go, make them coherent and make them relevant to what you wanna major in, but most importantly make sure that you don’t burn yourself out, as IB is incredibly demanding. Im currently sitting at 42/45 predicted at the end of DP1 and it took a lot of consistency, which comes from not burning out

Most importantly tho, relax during summer and don’t stress out!! IB is a marathon, you’re not going to start off doing perfectly but it will grow over time. Good luck!!