Professors, even in large lecture classes, are always approachable and friendly. They are open to extensions when asked and even small talk. However, with the amount of time you have with each professor (this also depends on the size of the class) it's unlikely for you to become very friendly with any teachers throughout college unless you take initiative.
Classes can range from 7 people to 200. There are a variety of options, usually intro classes are big while seminars, language classes, and specific topic classes are smaller. With large classes there is an immense amount of TAs that are always available to help. They also run review/discussion sections to allow students to ask specific questions and get advice from experts who already aced the class.
Most classes, in the humanities, make you do a lot of reading, have a smaller discussion section, and then 2-4 big assignments like midterms, finals, essays, take home exams, etc.
The variety of courses speaks for itself. There are too many choices and they are all interesting!