Refresh rates on eink are generally poor. But it seems uncommon to worry about Hertz or frames per second, because the advantage of low power usage disappears if they are refreshed at anything approaching "realtime".
For applications which need fast refresh rates and characteristics like good readability under sunlight, transflexive LCD displays seem to be more popular and economical.
Remember, eink works by physically moving 'ink' particles within each pixel using a magnetic field. It takes a lot of power and time compared to how quickly electronic signals usually propagate, and it seems difficult to get around that physical limitation.
Refresh rates can actually vary a lot. They're intentionally slow on book readers, because eInk is rather power hungry when it redraws, so fast refresh is not free. But for a dedicated display, it's not a problem, so e.g. Dasung jacks the refresh rate way up on their monitors. Take a look at e.g. typing and scrolling here:
The problem I’ve had is just how jarring the transitions are on refresh. I don’t need it to run continuously at 24/29/60/120 FPS, but I do want it to load the next page in like 25ms. So imagine it taking more power to update the display, but it still isn’t refreshing continuously so would hopefully still have power consumption advantage.
(Even a drawing application could maybe handle it if you could refresh subsections of the display)
At least for grayscale e-ink (Carta) displays they have this under control quite nicely. Full refresh isn't needed often, and when it's needed it's a fast rolling refresh rather than the traditional full screen blanking. Although I'm not sure if that is a reMarkable specific feature.
Ignoring the details of the physics and mechanics of how it would work of course :). My highest Physics grade was an NZ C+, so somewhere in the 55-60% range :)
For applications which need fast refresh rates and characteristics like good readability under sunlight, transflexive LCD displays seem to be more popular and economical.
Remember, eink works by physically moving 'ink' particles within each pixel using a magnetic field. It takes a lot of power and time compared to how quickly electronic signals usually propagate, and it seems difficult to get around that physical limitation.