Add noise features and true black lines

Hi

I'm a coloring my graphic novel and i have two questions 🙂

I really like the add noise effects...In a way it adds the grain we can find in analog photography,it is really lively..

But i really wish i could make the filter to have bigger dots...maybe less dots too...is it possible to edit it in depth?

I already tried different settings with the amount and gaussian mode but the pattern remains basically the same....

My second question is related to the second attachement ...when i'm isolating my black lines from the original drawing,it seems some white is still therejust at the border of the black line...is there something i've missed there?

Thanx in advance!

Lio