Should I take an S/NS grade during COVID19 if I want to go to grad school?
No one can predict how it will play out as the world of academia, as elsewhere, is in a bit of chaos now. I expect, however, that most people will be understanding of such things. They will need to be, in general, since a few universities are only "grading" students on that basis for now. 

But, I doubt that it matters very much which way you jump. Your description of the course indicates it would not be a major determinant of anything in your future. If you take the grade and are asked in the future, I think your description here would be fine, especially if you are doing well in other, more important, courses. 

That said, cum laude will be nice to think on thirty years from now.