You've got the original game with all its good points and bad. The bad is that the original 1.1 patch released way back in something like 2002 broke the AI in Instant Action mode. This 1.1 patch is now fully integrated into the GOG release meaning Instant Action (aka skirmish) won't work properly. I have an original copy and the only way I could get the AI working was to run the game unpatched. You can't do that with this release at the moment. The GOG modifications have upsides and downsides. I can run the game on Windows 10 without mods which is good. But the GOG modifications have rendered it incompatible with some community mods which is not. This game ended up a bit unloved and a bit broken. It was never supported that well after release and while this GOG version does get the game running, the old problems still remain.
