What does the ACARS Weight and Balance Request page look like?
As you said, it will vary by airline. Mine has a few screens, and the pilots enter in number adults and children in each seating zone, number of total infants, number of standard and heavy items in cargo, any additional weight in cargo (shipping cargo, mail, ballast, etc). Also the desired runways to get data for and their condition (dry, wet, snow, etc).
Many, sometimes all, of these items are auto-populated when the gate agent closes the flight, except for the desired runways.
When the response is received, it contains weights and center of gravity numbers, and then each runway will have specific thrust (temperature, ECS/bleeds, flex, and target resulting thrust) and flap settings, as well as the V speeds.