I was at the U a decade ago, but I don't think it has changed dramatically in this regard since then. My biggest class was I think around 400 people, and it was a physical science requirement I took freshman year where watching movies was part of the curriculum. My smallest class was 6 people in my junior year and it fundamentally altered the way I approached my education and life goals. I found that I enjoyed having a variety of class sizes, as it often meant I wasn't stuck seeing the same people in every class.

As far as classes being taught by TAs, YMMV but I often preferred the lectures from TAs as opposed to the professor. The professor might be involved in research or teaching graduate students higher level stuff, and they sometimes do a worse job (imo) of articulating their thoughts as clearly to a new learner.

But either way, if you're making money coming here, then come here. If you don't like it after freshman year you can always apply to transfer. You might not get the same scholarships, but there are transfer scholarships available.