Read a very interesting and thorough review of the braille display Active Braille 40 2021 by Scott Davert. Scott Davert is a Coordinator at Technology, Research and Innovation Center, Helen Keller National Center for DeafBlind.
The article can be found on the website of Helen Keller National Center for DeafBlind.
Automatic scrolling – be it truly time-settable and/or sensor-triggered – may be more of a nuisance than real help. One usually does not read like an automaton in pedantically regular increments. What I, after some 36 years of practice starting with Versa-Braille – considrr as most useful for fast reading is the reverse panning where you scroll forward with your left hand which is almost permanently positioned at the beginning of the line. My experience together with some French research suggests that, strangely enough, one can read fastest on very short displays (up to 20 cells). In 1990, I made a recording of Eureka A4 Manual using Versa-Braille 20 with no exertion as if reading from hardcopy. The automatic gimmickry makes Braille displays unnecessarily more expensive while the effect may not be worth the invested money.