@jasli98 you wouldn’t be taking the same classes with the same kids all the time. M&T doesn’t have special classes that only M&T students take. Would would be taking the same classes as all the people pursuing the same engineering degree as you, and the same classes as other wharton people. There might be one class that all M&Ts have to take to together, if any at all, not sure.
As for internally applying for the dual degree, the ideal situation is to apply to wharton first and then either at the end of your freshman or sophomore year apply to do a dual degree with SEAS. The reason for doing that instead of getting into engineering and then applying to wharton is that you need at least a 3.4 (more like a 3.5+ to have a good chance) to be accepted to wharton and 3.5 is not at all easy to get as an engineering student, especially because all the introductory science and engineering classes are curved very harshly. On the other hand your grades as a wharton student will most probably be quite better and on top of that you will need only a 3.0 or better to be accepted to a dual degree with engineering as a wharton student.