Almost every GUI action results in the issuance of a Tcl command. You can create an IP and set all the customization options in a Tcl script without user interaction.
You need to know the names of the configuration options and the values you can set them to. Typically, you first perform the customization through the GUI, and then create the script from that. After you see the resulting Tcl script, you can easily modify the script for your needs, such as changing data sizes.
Tcl script based IP creation is useful for automation, for example working with version control system. For information about source management and revision control, refer to this link in the Vivado Design Suite User Guide: Design Flows Overview (UG892).