There was a really good article shared a few weeks ago about video memory on old systems that didn't use a frame buffer, instead the video data was streamed to only a couple of bytes and calculated in real time. This had the effect of nearly zero lag because sprite location could be calculated right up until the moment the first row was drawn to the screen. I wish I could remember exactly what that article was.
A good example is the various parallax and scrolling effects in the intro cinematic to Link’s Awakening on the Game Boy/Color, achieved by changing various hardware scroll registers in the horizontal blanking interval (time between one line being finished and the other starting). The main limitation is that you can only do horizontal effects, not vertical.
I’m wondering if the article you’re thinking of was the Wired piece on the Atari 2600? That famously ran all of its game logic in the H- and V-blank intervals.