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It seems that the information provided is more than sufficient to understand the main differences between the offline versions of Heroes II and Heroes III. The remaining "minor details" can be "filled in" during the actual gameplay.
I'm saying this because it's not worth "exaggerating" the topic with a pixel-by-pixel comparison, as it's already clear that if desired, a vast number of such differences can be found, including in magic (a subtle hint that there will be no separate section for this).
In my opinion, excessive "bloating" of the article is highly undesirable, as it could lead to it being very difficult, if not impossible, to understand.
Everything should be read "in one breath"!