I decided to go with the five rows of eight digits.
So, each row is shifted through eight shift registers and shows up as 64 segments (counting the decimal points).
This is what five rows of 64 bits look like on the scope.
Yellow is the clock, blue is the data, and purple is the latch that is triggered as we switch rows.
Zooming into the first row, lowest bit is high while the other bits are low because on first row we set leftmost digit to 1.
zooming back out, after all 64 bits, you can see the "2" of the next row.
You can see that this time, second bit is high, while the other bits are low.
Subsequent rows are similar and on row 5, you can see the 0xFF as last 8 bits being shifted out.
I wonder how many people read this. Oh well, it was rewarding to see the bits set in a #MicroPython array refreshed by an independent timer so we're free to implement the snake without worrying about updating the display.
Shift register code to do this test is on github.