Color by bit position repeated every 2 bytes, or 14 pixels.
One can choose to store the data in weird ways that map to the screen, or use table lookups. From there, unrolled code can go damn fast too, and in all those scenarios, RAM is used to cope with goofy addressing.
Then comes 7 pixels per byte!
On the plus side, doing that, plus the high bit shifting pixels a little to provide a basic color attribute bit, meant getting a 6 color display instead of a 4 color one.
6 colors is enough to do basically anything. 4 is not quite enough.
But, that also means having to either shift data prior to blitting it to the screen (slower), or preshifting (faster), and more preshifted data copies are needed because the color by bit position repeats every two bytes, not every byte like pretty much all the other 1bpp + artifact, or 2bpp systems needed.
If one has the RAM, fact is the Apple did not have screen DMA wait states slowing the CPU down. That meant getting the best of 1Mhz.
It also made the system easy to accelerate too.
A 2 to 4Mhz Apple performs very well on software sprites.
But even the stock machine could deliver quite a bit more than one might expect, given things could fit into RAM.
4Mhz can deliver a side scroller on par, BTW. But, that would still be a RAM challenge to hold the diversity of images seen in something like Keen.