I’m not super experienced so take what I saw with a grain of salt, but I once read on a garden railway blog/guide site written by George Schreyer that most garden railway curves are so tight that keeping them perfectly level is better.
In my railroad I do have the outer rail raised a tiny bit (I don’t have the exact level but it’s raised a little bit) and I think it helps? I have some of the sharpest curves but then again I pretty much never run anything longer than a 40’ box car.
I guess it depends on what curves you have and what you run but I’m not sure. Hopefully someone else can give a better answer