Yes and Yes.
You can either have the XW-Pro only supply power to it's output side, or command it to "sell to grid" out the input side. If it is selling to grid, you would need to add the "Watt-Node" unit to measure the grid power. I am still running without a Watt-Node. In this mode, I can tell it how much power to push back out the grid input side. I just estimate how much the house needs, and when loads turn on and off, it varies how much may go out to the grid from my home, or draw some in if needed. This is okay for me as I have a net energy metering agreement that allows me to push out up to 16 amps, or 900 KHW's per month. When you add the watt node, you get another control page. You can set it for how much you want to allow it to export. The watt node will adjust the inverter power to maintain your desired current. It could be from always taking in a little current to pushing out current. If you need true zero export, then yes, you will need the watt node.
When the grid is up, you can always take any power needed from the grid. Your main panel is fed by the grid, and if there is no inverter, it all works just fine. What happens with the inverter is that is will supply power as well as the grid. In the case of the USA version of the XW-Pro, it can be set to supply up to 6,800 watts, about 28 amps on bother legs of the 120/240 split phase output. It will even supply up to 40 amps on one leg under a large imbalance. There are models for 230 volt single phase as well, and 3 can be grouped to make 3 phase. If you have it set for grid sell with the watt node programmed for zero export, the inverter will take battery power and convert as much as is needed to zero out the grid power. If the demand in the house exceeds the power limit, 6,800 watts in my case, then any current above that will come from the grid. If the battery runs down, the inverter may shut down, and then all of the power will just come from the grid.
What do you plan to use to charge the battery bank? You still need to get the power from somewhere. To get the most out of the Schneider system, you should have DC coupled solar to charge the battery bank. The XW-Pro can chare from the grid, but you have to manually trigger it to start a charge cycle. With the DC solar, it just gets charge current whenever sun is hitting the panels.