The most fun part of these projects is seeing people quickly build ad-hoc renderers for E-Ink. Very quickly you find out you need render passes, dithering, debanding, etc.
The one display I got takes about 2 seconds to cycle. You can make it shorter with partial redraws, but for my purposes, the cycle was the right thing to do.
2. It is in stock. :) Raspberry Pi Zero 2 and the waveshare displays are in a bit of a stock crunch, and the frame I ended up mounting this in, along with the special flat USB cable, pushed the project cost to the same price. It's my own aEsTheTic tho.
Here's my weather E-Ink board (which consistently gives a faster result than waiting for the iOS weather app to fetch & render): https://github.com/OmerShapira/theres-some-weather-outside