Bangsian Fantasy, in my experience, is not a very widely-spread subgenre. It can be set in a whole range of realities, from our reality as we know it to a reality very close to ours, to something that is purely a flight of the imagination. It’s one binding characteristic is the featuring of a historical figure from our reality.
Since I really can remember reading only one series featuring Bangsian elements, I will have to use it as my basis here. Orson Scott Card’s Alvin Maker books don’t actually focus on the historical figures, but they do feature here and there. These books use a version of the world where things have happened a little different to what we see in the history books. The description you usually see on his books refer to “a magical America that might have been”. Napoleon Bonaparte specifically features in these books, having the ability to make people adore and obey him – yes, a maaaagical ability.
Now that I think of it, I’m fairly sure you are likely to find Bangsian elements in Steam Punk books and movies…also in Dark Fantasy.
Wikipedia gives a few examples of Bangsian Fantasy I have never read, so, you might want to check that out too.