Castle Garrisoned Units

Does anyone know if units are garrisoned in the castle if the castle has longer range? When I stack Mangudai in my castle it seems the range is longer but I’m not sure so that’s why I’m asking. A lot of the posts I found talk about damage amount or number of arrows but didn’t find much about range.

Also, do regular castle arrows cause through damage? Like if a straight line of infantry is walking straight towards a castle is it possible for regular castle fire to hit the guys towards the middle of the straight line or just the first unit in line, and also does garrisoned units change this if regular castle fire does not cause through damage?