Impact of parameters in experimental results of paper
Actually, I had a programming part in my masters thesis in which I wanted to show that some parameters do not have significant impact on the results. This is what I did which seems to be a combination of your methods:

I drew a plot with all the parameter remaining the same except one parameter that I want to study on. Even if the variation of the parameter does not show any significant change in the results, it does worth to show the results in a plot. It is not important that all the lines overlap. At least the reader sees that the results are the same. But, in a paragraph or at least one sentence following the graph I would talk about this. You may write that all the plots overlap, because of this and because of that; and talk about why such results happen. Also, in the caption of the plot, write something that directly says something about such insignificance.