The classes will be different to a large extent. If you study for Main+Advanced then the focus will be more on difficult problem solving and how you can increase your problem solving skills. But in the mains course you will be taught with the mains specific problems and will be isolated to that portion only.

I would personally recommend if you want to join a offline class then go for MAINS+ADVANCED because you will get a broad sense of problem solving which will help you more to score high in Mains.

For JEE MAINS crash course you may visit the link below:

https://learn.careers360.com/knockout-jee-main-april/

To know more about JEE coaching from career360, you may visit the link below:

https://learn.careers360.com/

I hope my answer helps. All the very best for your future endeavors!