Hello dear aspirant.

Actually you have to make your call in this case but I can tell you about all three my point of view and suggestion.

Diploma in computer science is not a good option because it is not even equivalent to graduation it's value is of 10+2 level only you can opt for it when you were in 10.

BCA and B-tech both are good. BCA is a little easier in comparison to other one and BTech gives a high package and placement in comparison to other. B-tech is of four years and BCA is of three years. I suggest you to go for B-tech as a wise call.

Think and then decide.

Good luck