I think that for your GPA, you’re going to have to be north of 1500 in order to be real competitive for UCB. Almost all the kids that got into Berkeley from my kid’s HS that he knew was north of 1520. A lot of it comes down to your essays as well, there’s going to be too many 3.75-4.0 uw GPA applicants to choose from.
Declaring for CS may not help, as everyone goes in L&S as undeclared anyways. Hopefully you have a ton of AP classes taken or already taken.