In Bangladesh, we had 3 seating arrangements on our trains. 1st class, 2nd class and 3rd class. You will get small cabins for 4 to 6 people in the first class. There you will get AC, beds to sit in and sleep in, a small table, and a window. No hockers (people who sell items to the travellers) will come. You can order food from the train's food compartment/canteen, which they will bring to your cabin.

I didn't like this situation. It's true it will give you some private time. But I like to be offered tea, snacks, and items every few seconds by the hockers! I don't want to go somewhere to order from the limited food items. That's the choice of a foodie person.

Second-class seating arrangements mean you will have chairs/sofa the same and organized like a plane, except for the food and magazine trays.

The 3rd class sitting arrangments are long sofa, no partition from in 3 person's seat. This will be the best solution if you plan to book a whole compartment for a group tour. And of course, every second, someone will come and try to sell something like tea, toothbrush, medicine, etc.