Each game according to Cesar is around average adventure game length, with the 1st and 3rd games being around KQ5 length and the 2nd being around KQ6 length.
Not sure what you mean by original game. Originally KQ9 was supposed to be one game but it became too big, so now KQ9 is actually made up of 3 different games. Think like the Lord of the Rings movies.
1st game: You control Graham
2nd game: You control Rosella and Alexander
3rd game: You control all three
There was a lot more revealed in the chat, but I can't remember it all, so make sure you read it when it's posted.