I‘m really happy to contribute to this discussion by telling my story.
When I started studying a few years back, I had nothing but an outdated iPhone 4 and an old gaming desktop PC.
I‘m a student of the humanities, and I quickly realized that a proper computing setup was key for optimizing my productivity. I never needed more than Word/Pages and a proper PDF application, but I never considered going iPad only, even though the first device I bought for my study was indeed an iPad Air 1. I read hundreds of PDFs on that thing while sitting comfortably on the sofa. A Laptop couldn’t have done that for me. The amount of reading for both my major and minor subject was always going to a problem for me, and the iPad solved that. But it never became more than that.
When the first long papers were due, I bought a MacBook Pro 15“, because neither the iPad nor the old gaming desktop I mentioned earlier would cut it. Too loud, too stationary...and the awful Windows 8 on top. The iPad on the other hand was too small and there was no full version of Word available back then.
The 15“ screen of the MBP was more than sufficient, until I had to write my 40 page Bachelor‘s thesis. I was juggling with dozens of PDFs and always had to use cmd+tab to switch between the windows, which costs more time than I imagined. I bought two adapters and hooked up the two old monitors I had on my old gaming rig. I‘m still grateful to have that shabby old 19“ 4:3 second screen exclusively for my sources/PDFs, while my main display is for Word only.
So what’s the moral of that story? I almost took the whole 3 years of my study to find my perfect computing setup, even though I didn’t have any special (software) needs. I may be a little spoiled now, but I would never even start to write a 30+ pages thesis without my dual monitor setup.
Can you study only with an iPad? Sure.
Should you? My answer is no.
No matter how basic your needs are, the iPad, with all its limitations (small screen, iOS etc.), is not a PERFECT all-in-one productivity solution. It‘s great for taking notes, reading and annotating PDFs, and doing some creative stuff with the new Apple Pencil, and that’s about it. If you accept its limitations, an iPad can be a powerful supplemental tool for your study. Effectively taking notes and reading PDFs was an essential part of becoming a successful student, at least that’s my experience.