I run one screen, so I have the main take up about 80% of the area and the other four are stacked on one side, so that the screens are somewhat square-shaped.

Which setup works best is subjective. Try a few different setups and find which works best. One account on each screen might be best but it might also be more difficult to follow, or be more distracting. Or if the monitors can be rotated you might find it better to have the second and third accounts stacked on one monitor with the main on its own. And so on.