Laptops are incredibly useful for university no matter what you take. You pretty much need access to a computer given how much homework gets put online or how much projects require computers to do, so you may as well get one that you have with you all the time. If you don't care for paying for textbooks too, you can usually get them for free on your laptop and actually save money (if the professor's nice they might even give you the link directly) as long as they don't require stupid activation codes. And being able to kill time can be a godsend if your classes are spaced out much.

I can't really comment on difficulty directly, I'm not taking it but my cousin is a professor in it. What I've heard is that a few courses are bio-level difficulty that make-or-break most students, while others are bird courses you don't need to worry about.

How universities organize labs would depend on the university. Generally they'll want you to review notes or lab instructions beforehand, but usually you don't actually need to if you remember most of the recent lectures. You can (but shouldn't) be late for classes but always try to be on time for labs--no one gives a fuck if you're late to class but your lab instructor and partner(s) will get pretty annoyed by it.