AC1 will be fine. I did exactly this trip from Mumbai to Agra in February, no problem. You will be sharing, possibly mixed sex in a sleeper. At no time did I feel unsafe or uncomfortable. You will get a meal (choice of meat or veg). It's a great way to meet people and to see the countryside.

AC1 for my trip meant a lockable 4 berth, so the only worry would be the people in the cabin with you. No security issues at all really.