There’s plenty of tolerance and diversity of opinions in all UC’s in general, and most particularly at UCB. My UCLA kid is ChemE i.e. south campus, so he doesn’t have many classes, such as humanities, in which there is a lot of debates going on, but I’ve never heard any negative from him about it.
Some intro lower division classes will be very crowded. I think the largest class at UCLA for my kid was maybe 400-500 people. I’ve been told of CS and bio classes at UCB being 1000 students. But he said most of his upper division major classes are about 50-60+ people. I think UCLA does a good job of guiding students to graduate in 4 years, there’s plenty of help and guidance if the student seeks it. Same with knowing professors and TA’s, you need to make the effort. He did tell me there was commonly a line of students for office hours. That was news to me, I went to office hours plenty at UCD and never had to wait (over 30 years ago!)
A negative would be my kid has told me how hard it was to get into the engineering career fair, that it was a multi-hour long line just to get into the building. UCLA has the highest student population in the smallest land area, so it’s crowded. I haven’t heard much else from him about career guidance, he’s pretty much does it on his own.
If your kid is self driven, able to advocate for themselves, seek help when needed, then they’ll be fine in the UC system. All the kids there are bright and motivated. Another frame of reference, my kids went through public schools entirely. When I spoke with other families with high school kids in private schools (common in bay area), I was surprised by how much the counselors did for them, and all the hand holding involved. Our public high school counselors actively discouraged kids from taking AP classes, and really did the absolute minimum. They only cared about maintaining graduation rates, and not college guidance. So from that perspective, it’s way better now my kid is at UCLA. The help is there but you do need to seek it out yourself, there’s no hand holding.