Greetings. I followed the guide on GoG to install the games. After installing the widescreen mod suggested by gog with the given parameters of 1680x1050, the game launches in a different resolution. What am I doing incorrectly?

I'm using the shortcut launch baldur's gate 2 complete. Is that the correct one?

That's a terrible resolution for Baldur's Gate. However, it's your choice, so I will just say that load order is important for the Widescreen mod. Please post your Weidu.log here.