Dig this BATMAN DAY special: Over at 13th Dimension, we take almost 80 years of Batman history and boil it down to the essential storylines, characters and elements — so that you can make your own canon:
https://13thdimension.com/the-ultimate- ... ity-guide/
Check it out if you like!
The thing that makes Batman so interesting is the different canons, versions and everyone like you said have their own interpretation of the history, especially the alternative origins of the Joker. Didn't he once say he couldn't even remember which one was true, just uses the one the person he tells believes ?