If you are wanting to run two separate pieces of code for different models of cards at the same time, this is what I would do:
1) Create a separate sequence file for each card
2) Create a master sequence file to run the test. This master file would have two Sequence Call steps in it. Each one would reference the MainSequence from one of your sequence files from step 1, and each sequence call would be set to execute in a new thread.
In TestStand there are always multiple ways to solve a problem, but this is a simple approach to what you're trying to do and should get you started on it. The advantage to putting the tests for each type of card in a separate file is that it logically organizes your code and makes things easier to develop and debug. You can work on each set of tests individually and be confident that they do not have unknown dependencies on each other.
I hope that helps, and let me know if you have any further questions!