1. UM01 cards are those that are issued by Unitymedia by default, i.e. if you subscribe to digital TV. They are compatible to the receiver you are getting from UM, and with all Nagravision-enabled receivers. Also, the Alphacrypt Classic can read those.
I02 cards are for some other receivers available on the market, i.e. some HD boxes. See page one of this thread for an overview.
You can get an I02 card from UM as well, but you will pay some more money per month for this card.
If you are subscribing to Premiere, you just ask them to activate your subscribed channels on your UM smart card. They will do that, and so you don't need to swap cards all the time.
Also, Premiere HD is broadcasted by UM, you just need a HD receiver for that.