E-ink's quality and refresh rates are inversely related. Whilst generally it's preferable to use a high-quality mode and slow (0.25 -- 4 Hz) refresh rate, refresh of as high as ~8 -- 16 Hz is possible. Video and animation quality here are not great but they are usable in a pinch.

Video of an Onyx BOOX Note displaying video, which I can vouch for from a similar (Max Lumi) device:

<https://yewtu.be/watch?v=XRDJv_-wWBI>

For a relatively static GUI display (such as the Classic Mac), e-ink displays are in fact viable, and there are e-ink devices sold specifically as computer monitors:

<https://shop.boox.com/products/mira>

For a demonstration of the capabilities of various e-ink displays (least capable are first), see: <https://yewtu.be/watch?v=KdrMjnYAap4>

I'd want a B&W, line- or halftone-oriented graphics, and relatively static window placement in general, with paginated rather than scroll-based displays (that is, content updates a full screen at a time rather than scrolling). It's not that scrolling isn't possible, it's just that it's really annoying. And there's a reason e-ink devices tend to use line drawings or etchings as demo / sleep screens (see Diaspora* post below for example).

I've written numerous times on HN about what the benefits and affordances of e-ink are, e.g.:

<https://news.ycombinator.com/item?id=31396797>

<https://diaspora.glasswings.com/posts/638a8d10e041013afba844...>