If you’re not sure, I’d say try the dlc on default mode first. If you ever find yourself feeling like you’d enjoy the game more if it was less scary, you can turn on the reduce frights option.
I played on default, but from what I’ve read it reduces certain sounds and the chance of certain events happening. Of course I don’t want to say too much because just like the main game, the magic is in discovering everything yourself :)
Lol this screenshot brought back so many memories of playing this game as a little kid!