Another thing that confuses people who are building inverter systems is that the manufacturers are misrepresenting this in their settings.
For split-phase configuration, the setting is labeled 180. But the inverters are not actually 180 degrees out of phase.
They are always in phase with each other.
The only difference is that they are either wired in parallel or series.
Parallel equals twice the amperage. (At 120v)
Series equals twice the voltage. (240v)
Series with a center tap equals split-phase. (120v/ 240v)