You'll find here a description of the 3 modes:
If you are not sure about the Network it's better to choose Maximum Performance (the default). By that way the Primary don't suffer from any delay in writing the redo to the Standby.
With Maximum Protection the Primary is unavailable if the redo cannot be sent to the Standby.
Maximum Availability is a go-between these 2 modes.
Anyway, think about monitoring the redo application on the Standby so as to avoid any GAP. Also, you can set the parameter "archive_lag_target" to force a switch of the redo at regular interval.
Hope this help,