Has the refresh rate on eink devices reached like 30-60fps?

It definitely looks cool and I might give it a try, but I do love my dark mode and color syntax. My understanding is that color on eink is pretty limited. It also isn't worth it to me if I'm going to be spending $500+ on a "monitor". But I'd definitely love if things moved in that direction.

Honestly if Apple wasn't so insistent on making the iPad not a general purpose computer I'd use that as my thin client.

They are still not great for high refresh rate, but I have a boox note air4C that can do fast-enough for video. It gets some ghosting (although it should be minimal for typing as you are fully changing from white to $color, backspaces might be a problem though). You will need a full refresh when scrolling but that is fast enough.