I feel like no one has given you depth on each school, so let me try to help you out:
Vanderbilt:
GPA - The average applicant has a 3.8 unweighted, 4.25 weighted. You are above average in both of these, significantly. So you should feel good about your academics.
Testing - You’re slightly above the average 31. They weight grades and test scores pretty equally so this will help you as well.
Extracurriculars - While you certainly have good activities, Vanderbilt also considers talent & work experience. I don’t see this in your list, but if you do have a particular calling/job, elaborate in your app. They weight activities on the highest scale with grades and scores.
Admission - Vanderbilt only takes 10% of applicants. This makes it hard for anyone, even the most qualified applicant to get in. I’d say this is a reach school for you, but you are a strong applicant.
Duke:
GPA - The average applicant has a 3.8 unweighted, 4.32 weighted. You are again above average in both of these, nice!
Testing - You’re slightly above the average 31. Like Vanderbilt, they weight grades and tests with importance, so this should help you.
Extracurriculars - Duke also weights activities on the highest scale with grades and scores, considering work experience and admire talent/ability.
Admission - Duke only takes 10%, which again makes it hard for any applicant. This is a reach school for you as well, but you have strong stats.
Georgetown:
GPA - The average applicant has a 3.76 unweighted, 4.2 weighted. You are well above average here.
Testing - You’re slightly above the average 31. Georgetown weights grades and scores similarly, so this should help.
Extracurriculars - Activities are important at Georgetown but considered slightly less than stats. Volunteer work is weighted equally to activities. If you’re a good interviewer, try to get one, because they consider this as well.
Admission - Georgetown takes 16% of applicants. Again, really competitive, but I’d say less of a reach that Vanderbilt or Duke. Fair match/reach.
Northwestern:
GPA - You’re above the average 3.8/4.29. Yay
Testing - You’re slightly above the average 32. Grades/scores are weighted both with high regard.
Extracurriculars - Though weighted slightly less than your numbers at Northwestern, focus on highlighting your talents.
Admission - They take 10%. Very selective. I’d say this is a fair reach/reach.
Overall: You are a strong applicant for any of these schools, and I think it’s great that you have picked some dream schools. Your stats and strengths will set you aside from many other applicants especially if you sell yourself in your application. Make sure you also find dream schools that you’d be just as happy to go to that are a bit less selective. Schools like Tufts, UVA, Tulane, Amherst, Northeastern, are all extremely good schools and similar to the ones you’ve listed. Best of luck