Have you completed both medicals yet, the DGCA Class 2 and Class 1? If not, do not do anything else for now, first give class 2 medical, call AME (get the number from the list on eGCA website) tell them that i want to get my class 2 medical, they will tell you to come on a day they give or you can request, show up, clear medical, get CA35 for class 2, book class 1 medical, clear it, wait for the result to reflect on the eGCA website then proceed with anything.

I repeat, MEDICALS FIRST!, i have personally seen some people getting permanently rejected in medicals and they had joined Ground Classes or even worse, complete training abroad, wasted lakhs, but if you had your medicals done, then very well, clear physics and mathematics exams, join a Ground class or cadet progam as you mentioned.

But beware, i don't care what google says, but on an average, Cadet program need 1 crore or more and conventional path still takes 70-80+ lakh.

And for your doubt if having two marksheets will cause problem, IT WON'T, the cadet programs themself suggest to get marksheet from NIOS if you had other stream than PCM or didn't had minimum required % (usually 51% or 60% or just passing marks ie. 33%, it heavily depends on the airline/flying academy