Multigrid ESS and 3 AC coupled Inverters - all same phase and ACin?

Txs Trevor. I did watch the video 8.1 (which I had in the past already) but it doesn’t answer my specific question unfortunately. It is still unclear to me if I have to connect all PV AC inverters to the same phase or not, if I run a single phase system. Or do I have to configure a three phase system, using one multi only? I am not talking about wether using ACin or ACout, that difference is clear to me and I might consider moving one PV AC inverter to ACout (Option2) , but still - the question remains. Same phase or not ?
Maybe I missed the point so far, so please let me know.