What do you mean by "cd + ss card"?
A US turbo duo can play Japanese CD and SCD games, but not hucards, games w/ custom CD cards, or ACD games.
If you get an adaptor and the appropriate card, you can play anything on a duo but Supergrafx games.
the ACD format was the last upgrade to the CD drive for the pc engine. There were 2 cards, the pro for separate units, and the duo for duos. There were only a few games, mostly SNK fighters, but a few other goodies (especially saphire)