The difference between 2 wire and 3 wire is the 3 wire are capable of switching higher current, for e.g. they have a NPN or PNP transistor output and they can pick up a relay, if needed.
The 3 wire are either sink (NPN) or source (PNP).
The two wire is used for low current required inputs, such as a transistor or opto input device, and can be used in source or sink mode.
The voltage range is shown on the device or the manuf. literature.
Al.