DrakeFox: I don't know about the Steam release, but this is definitely an emulated Playstation version.
Also by default, the emulator seems to have mixed up binding of square and triangle buttons.
Thankfully you can hit escape to go to a rather bare-bones emulator menu, but it does allow you to rebind keys or controller inputs.
mcnichoj: Honestly the best thing to do is after installing it is to swap out the pre-packaged emulator with your desired one. Saving via the normal save function doesn't work on their emulator and the settings aren't optimized to make it run and look as good as it possibly can on modern hardware with proper emulator tweaks.
Stupid question, but where IS the ISO? I'm looking in the game installation folder and can't find any bin/cues, chds, or large files that would suggest it being the iso.
EDIT: I think I've found it. It's in the Res folder, as "game.bin" and "game.cue"