I debated the same thing when I was going to grad school. Ultimately, I think a really nice notebook and a set of pens works better.
The ability to lasso text and move it around is really nice though. And marking up PDFs is really nice. I just missed the ability to use different colors and quickly flip back and forth between pages.
Now, I use it for work, but I'm still kind of preferring a physical notebook for similar reasons.
I do love the device and think it's the best digital eink device for writing, but (for me) I still debate picking up a physical notebook.
All that said, if you've got an iPad, maybe try using that first if you want a taste of digital note taking. If it works for you and you just hate the feeling of the pen, reMarkable may well be worth it.
To your other questions, I haven't tried using it as a storage device on other devices, so I don't know. Your files are synced to their cloud, so that's definitely one way to access your files on other devices though.