> I want my eyes to scan across the text rather than ratcheting from one word to the next word, which is both slow and exhausting.
An interesting experiment is to try reading a word at a time, but without moving the eyes. Here's [1] a command line program that takes text on standard input and displays it one word at a time in a fixed position on the screen, holding each word for N milliseconds (3N milliseconds if there is punctuation) where N defaults to 250 but can be set on the command line.
At the default 250 msec per word I found it very easy to read the material I tested with (random extracts from a Project Gutenberg edition of"The Valley of Fear", by Arthur Conan Doyle). That works out to around 160-180 wpm. (Not the 240 wpm you would expect from 250 msec/word because of the delays for punctuation).
At 200 msec/word, it still feels like a very slow read. Rate was around 270 wpm.
150 msec/word gave around 320 wpm. Still not a problem keeping up.
120 msec/word pushed it up to around 380 wpm and it starts to get hard for me. If I don't quite catch a word and have to think a little to figure out what it was I can get distracted enough to miss more words unless some punctuation comes up soon to give me a little break.
100 msec/word, around 480 wpm, is still reasonably comprehensible but at that point requires a lot of focus and feels tiring even though my eyes don't have to move. Sometimes not moving can be as tiring as moving when you are trying to not move for a long time.
I would not want to read a lot this way, but there are some places I wish it were offered. Many music players for example if the title does not fit in the space available autoscroll it back and forth. It can be very hard to read it while it is scrolling. A word flash display might work better there.
[1] https://pastebin.com/70eYTDkk