Would a school specific letter of rec help that much in your opinion?? (If you yourself have first-hand experience with this, that'd be awesome). I'm only applying this fall but I'm going to get my letters organized by about April so I can have them in by the end of the academic year in June.
Any input is greatly appreciated

Stats wise I'll be close to a 3.8 with a 166 and a 172 re-take. I don't have one school I'm set on going to, but I think Berkeley is my top choice because I want to stay in California but be able to work anywhere potentially.
Edit- Also in your opinion would it be ok to have all the letters be from professors, or should I get one from a past boss?
Thank you!!!