Not sure about the older Alphasmarts, but the Neos have pretty standard laptop keys. The display contrast isn't great, but it's not terrible like the late 80s/early 90s graphic LCDs. The small footprint compared to a current laptop is nice.

I'm also building something like what you are thinking about with an old intel NUC mounted on an even older LCD monitor and running Xmonad. It's a surprisingly fun project. My notes on the build are here: https://hackaday.io/project/174680-distraction-free-linux-ba...