Looks like a nice board - the price seems a bit high but I presume that you are in the EU and they are far less common there. I am mildly surprised to see a US ANSI layout on a Greenock board but I have had a couple with that layout here in the US.
Either plug should work but if your motherboard has native PS/2 you might as well use it. Remember not to hot-plug a PS/2 and allow it to be found on boot-up.
The Control key is one of the most often missing and least common spares, but you can use it as-is with no problem whatsoever.
Thanks. You are right about the price. Because of the mandatory import fees + huge S&H the whole shipping cost would be at least 100$, therefore
Any keyboard from eBay US would cost me more than that, even if it is 10$. So there wasn't really an option for me in the sub 120$ anyway.
Now, this board definitely is not very common, it is a made under the Lexmark brand, but it seems to follow all the previous IBM standards of that time (detachable cable, US layout, etc). I hope it is as good as it looks like and that there is not any funny business with it (like being a model that is using various parts from various models). I'll make sure to make a thorough post with details about it when I do get it.