Quick question about this format:

The article mentions that many different configurations can be made from the expansion chips, but does that mean I can also use multiple of the same expansion chip?

I.e., is an entry that uses two Y8950 chips legal?

i'd say most likely no, unless there is some dual setup that was actually common on the real hardware - i'm not an expert on this, there could be! but for now i'd say probably don't do it