Can one prepare for JEE Advanced by self study and using online programs (like Etoos, Unacademy etc)?

Friends, I am looking for your help here. My cousin has just appeared for Class 10 Boards. He stays in a district town in West Bengal with his family where there is no coaching center for JEE preparation.

He has shown great interest in Physics and Mathematics and loves solving their problems. He has appeared in SOF Olympiad exams and reached Level 2.

Context - I am thinking about his way ahead in 10+2 for JEE preparation. Way back in 2006-08, I had prepared for Engineering entrance through self study due to financial constraints of my family. I didn't crack IIT JEE but I had cracked AIEEE and got into a NIT.

Much has changed since then, particularly in the domain of Internet and availability of online resources. What is your view on preparing for JEE Advanced through self study mode and using online programs - would this give him a good shot at cracking JEE Advanced and securing a seat in an IIT? Also, which online portal is the best for JEE Advanced preparation?

If u are looking for online etoos without doubt is best