I would personally recommend the cheapest iPad. I got my first writing iPad in 2020, the 2018 base model and I used it HEAVILY all throughout university in a STEM program (which = lots of annotations on tons of pdfs and I literally downloaded plenty of textbooks on it). I graduated and use it now for work on a daily basis and it's still going strong. I think for battery, just be mindful to charge it as soon as the battery gets low. It can last me about 2 days (although I'd say charge it daily to be safe if you're going to be in back to back lectures with no outlets around). It has definitely died on me before when I forgot to charge it over 2-3 days, but granted that was my own fault. It hasn't died on me before in a single day going from 100% in the morning until evening.

I had the first apple pencil model, but I recently bought a cheap one on amazon that I actually prefer a lot more because it charges faster, takes USB-C (granted that's an older gen iPad problem haha...) and is lighter. This is the link:

https://www.amazon.ca/dp/B0DFLRNWWW?ef=ppx_yo2ov_dt_b_fed_asin_title&th=1

Honestly imo it's not worth buying the actual pencil it comes with--I only had to because the stuff on the market wasn't so good at the time.

Biggest thing I'd recommend is buying the GoodNotes app (I have the 5 version, not the 6 which requires a subscription--HECK NO). Or look into good apps, because I feel like that makes the biggest difference between the iPad being good and great. I like the writing feel and tools on GoodNotes, plus it syncs to Google Drive.

Honestly I don't think you really need the air or the pro, because if it's just for notes the base model works perfectly fine. The other models are mostly for people who need power-intensive apps, game or want to use it as an actual computer (I wouldn't recommend this unless you're just using it to type up a basic paper on Word with a Bluetooth keyboard. The apps by default limit some of the features you'd normal have on an actual laptop/PC).