HotA - General Questions and Discussions

A question arose, and it's difficult to verify myself, perhaps someone knows the answer. How are artifacts generated on random maps? For example, if I find the second Crown of the Magi, does that mean that the second "round" of artifacts has begun, and at least one of each type is already on the map? Or is the concept of a "round" only applicable to artifacts of the same value? That is, the second Crown of the Magi indicates that the second "round" of relics has begun, while other types of artifacts may be present even in the first "round"? Or is there no such concept as a "round" at all, and are artifacts placed randomly? Perhaps the developers of Heroes of Might and Magic know for sure, as they have a deep understanding of the game's inner workings.