isql and iqisql are the same utility with different names. The isql utility is a command-line Interactive SQL utility that uses the Adaptive Server Enterprise Open Client API.
For syntax and parameters, see the Adaptive Server Enterprise documentation: Adaptive Server Enterprise 15.5 > Utility Guide > Utility Commands Reference > isql.
Neither isql nor iqisql let you create user-defined database options. If you need to add your own database options, use the dbisql Interactive SQL utility instead.