I use the iPad 9 for notes and textbooks, but I sometimes wish I had gotten the Mini 6. It’s probably the perfect size for notes, but it might not be great for reading PDFs.
I wouldn’t recommend it. The screen is just too small for comfortable note-taking, especially when you need to take notes while looking at something in split-screen mode. The Air or Pro would be a better option. If you’re not stuck on iOS, check out the Surface Pro. I use the Microsoft Pen with my laptop, and it’s much better than Apple’s.
I love my Mini, but if you’re mostly taking notes for school, go for the iPad Air or Pro. Thinking back to my college days, the Mini would’ve been too small for me. But it depends on what you’re studying. I use my Mini for quick notes at work, and it’s great for that, but for school, I’d choose something bigger.
Yes, if you have a laptop or MacBook. If not, it might get frustrating as your main device. The battery life isn’t amazing either, but I use mine as a notepad and it works fine.