The xw+ which is what I assume you are talking about has two ac inputs. I don't know whether that requires 3 phase input from both the ac inputs if it is in 3-phase mode or not. The install guide could tell you.
With grid-tie, it is connected for a 2-way communication with the grid, so you don't need batteries. For off-grid use, you can also draw power from the grid, but you can't push power back on the grid, so you don't need batteries. If you are not going to use the grid at all, then you will want batteries or else you have to run the generator all the time unless you have another power source like solar that can cover all of the demand, and you will still need batteries in order to cover the under voltage during the time it takes to fire up your generator and get stable current.