Hi there,
Hope you are doing well. Yes, the option entry for MBBS as well as engineering will be at the same time in case of K-CET. There will be separate sections like medical, engineering, veterinary, and you need to enter the options separately in each sections but at the same time. The results will be announced separately for engineering and medical. Depending on which field you are interested in, you should choose either medical or engineering. I hope you got the point after reading this answer.

All the best.