There's been a huge amount of discussion about what Titanic's "true" horn sounded like. The one in the Simulator is probably as close as it is possible to get, as there is absolutely no way of telling how the horn would have sounded exactly.
The gentle blowing of the restored horn which was not attached to the mass of Titanc, nor plumbed into the entire length of the original piping, with all its twists and turns, etc is no indication at all, unfortunately.
So any discussion about how realistic the one in Ship Simulator may or may not be is purely a matter of opinion. Lots of opinions, no facts. Shame, but there you are.
As the other vessels aren't in Ship Simulator, discussion of them is a bit academic, I guess.