I think this is the same as the steam release, which is an emulated ps1 version.

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.

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.

I agree that you'd be better off using your own preferred emulator. But I did find the pre-packaged emulator fine. Didn't have any trouble with saving though. Might be down to the fact that I don't install Gog games to Program files, but instead to a separate folder on a separate drive, so the admin requirements to save are thankfully less of an issue :-)

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"

Any idea how to change the emulator?!

Right click the game in your library then do these steps:
"Manage installation"
"Configure..."
"FEATURES"
Click the third box that says "Custom executable / arguments"
Click the purple text that says "Duplicate"
Then click the box for "File 2" which will allow you to select any file on your computer to launch when you click the "Play" button on GOG.
Just remember to select the "Default executable" bubble under your new entry before closing the window out by hitting "OK".

Only downside is you'll be stuck with the yellow arrow next to the play button saying it couldn't sync your save file. You'll have to manually back up your save files to a third party cloud service or an external drive if you're worried about losing it.
The upside being you have way more customization options for a better gameplay experience.