I would lower it to C or C-. Ws can look particularly bad if one has a very high GPA because it makes it seem like the high GPA is artificially inflated (ex. Correlates with seeking out easier profs, etc.) and or the applicant is motivated too much by numbers
I would go as far to say that Ws look worse for somebody with a 4.0 than below a 3.5
Multiple Ws for sure, but idk about just 1. I have two pass/fails on my transcripts for courses where I ended up with an A-. To be clear, I didn't pass/fail them because I got an A-, but because at our uni you had to choose pass/fail at the beginning of the semester, and I just didn't feel like putting any effort into either class (they were known to be hard) and I didn't expect to still end up with an A- (and you can't revert pass/fails at our uni).
At 10 interviews, not once have these pass/fails come up, and my interviewers have typically even commended my extremely strong academics. Of course, there's multiple differences here between my situation and OP's. My pass/fail was not in pre-reqs, although one was science related (an advanced statistics class). Additionally, pass/fails are different from withdrawals.
Seeing a W on an application with a 3.9x would scream neurotic to me.
Totally understand, and at the end of the day, this is just personal opinion. I see taking a W and then getting an A in biochem as much superior to getting a C and then an A.
@voxveritatisetlucis I would not lower it to C, because from what I've been told, a W typically indicates you got a C or lower. I believe a few adcoms on this site said that they typically read a W as a C (but I don't really remember so don't quote me lol). Therefore, I would say a B is better than a W, but a C is worse, because while an adcom might subjectively view a W and a C as the same, the C has a tangible impact on your GPA, while the W doesn't.