The only difference that I remember was that they replaced Catapult with other units.
I'm glad someone tried to fix it, you should definitely play the remake version if they bring back catapult

I have repeatedly beaten the game with the mod - I have to say it's fantastic and I really appreciate devs' efforts!

The mod was improved vastly over time and I see no point in playing the original unmodded game any more.

So I just downloaded the Knights and Merchants from GOG but how do you add the remake to it? Can someone tell me how I go about doing that?

Hi. You can download KaM Remake latest version from the link posted in the first message in this thread
Visit the website (with downloads)