Hi,
For this purposes you can adjust your map to match the desired effect. Attaching screenshots showing two
Gradient Ramp maps with different
Noise values combined inside of a
Composite map (or
Mix map). This way you can tweak your
Distribution Map final look.
Also feel free to check
this post regarding possibility of "painting" your custom
Distribution Map using the Viewport Canvas tool.
To control the scale please double check you have the
Map check-box enabled, you are using corresponding
Map channel and
Min / Max limits are properly set.
Kind regards,