A: PSIM’s SPICE module provides convenience for users who must use SPICE models in their simulations. With this module, users may capture PSIM schematics, and run LTspice simulation. Users may also use pre-existing SPICE netlists (either written by hand or captured from other softwares) in PSIM schematic, and export SPICE netlists from PSIM schematics. The SPICE simulation runs totally within the LTspice engine. All the advantages and shortcomings of LTspice will be the same.
The SPICE Pro option (discontinued with v2020a release) was part of the SPICE module. This option was developed in cooperation with a 3rd party developer. The SPICE format in this option was based on NGspice with a few Xspice functions. The “Pro” addition to this option was to include some special models developed by the developer. Those models can be recognized and simulated with this version of SPICE only, and can not be used in other SPICE based softwares. If you have already have SPICE Pro on your PSIM license, it will still function with PSIM v12.