It sets the proportion between visual and textual control. So it determines how much of the generated render will be influenced by your canvas, over the prompt you wrote.
Drawing influence allows for you to decide how much you want your original artwork to influence the generated result. This is a good way to explore the relationship between your prompt and original sketch.
However there is a difference in behaviour when it comes to the two modes of VIZCOM
In this mode, you control, how much of the sketch lines will be followed by the generated rendering. It’s recommended to use high drawign influence for exact control over the results.
Recommendation: 80-100%
In this mode, your lines, design, and proportion will remain the same. Marginal changes are going to happen if you start decreasing the Drawign influence level. Below is an experiment with a render and a simple black & white brush stroke edit on top of it. It is interesting to see how the painted area is becoming an integral part of the design.
Recommendation: 0%-60%