Below is the differences between Client and Server.

ProWORX 32 Online Only Client (when not connected to a PLC) includes:
Write to the PLC
Read from the PLC
PLC Status and Analyze Device
Stop/Start PLC
Change Comm. parameters.
View documentation

ProWORX 32 Online Only Client does not include the following unless connected to a PLC:
Viewing and changing Traffic cop, ladder logic and register editor.
Emulation mode is not available.
Change/edit documentation.