Let's say there was a card that states that you cannot play it if the card preceding it has the same keyword.

Now, my question is, let's say the only card in your card pool has "Combo (mid attack)" in it, and the card you want to play has "Combo (high attack)" in it.

Are the two treated as if they have two different keywords? Or because the word Combo is on there, they would be regarded as having the same Keyword, regardless of its parenthetical data?

The keyword is Combo (X) . Just like Multiple: 1 is the same keyword as Multiple: 2 , combo is combo. One keyword, different reference points for activation.