For available XSPICE code models, please have a look at the ngspice manual, chapter 12 (see Ngspice, the open source Spice circuit simulator - Documentation: manual and control flow). About 70 models are available (analog, digital, hybrid). However some user action might be required to make use of these models.
An example (analog multiplier) for KiCad 7.99 is given at More simulation examples for KiCad/Eeschema/ngspice .
A generic OpAmp (including its model) is available in the Simulation_SPICE library of KiCad 7.99.