I think cards will be unique to the grasslands board only, since instead of holding cards in the space one, everyone collected rocket pieces (and those pieces were put in the spot where the cards went)
As for the effects of the cards, there looks like there are two different kinds separated by colour.
One type lets you use it on your opponent, and as for the other, I'm guessing you can use on yourself.
It also seems like you won't know what the card does until you use it, so is there a possibility that cards could give your opponents an advantage if unlucky?
...BTW, in the video, we also see another card being used were Lakitu steals a card from Wario and give it to Mario.