One - without two way switch - if the one way switch is opened, other home utilities doesn't receive main supply.

Two - with two way switch - if the one way switch is opened, other home utilities will receive main supply, when two way switch shifts towards main (manually

only during isolation of inverter during maintenance or inverter fault)

From these two circuits, you will get some idea about the purpose and importance of two-way switch in a Inverter cum Mains supplied areas.
In case of inverter fault, open the one way switch and close the main side switch in two way switch, by the way, during maintenance, supply from mains won't be interupted.

 

your two way switch most certainly would interrupt mains powered devices. with contact bounce included it is not possible to switch between power sources by hand and not have a long( by electronic equip. standards) interruption in power. also there is arc damage on contacts if switch is moved while large currents are drawn.