Deadheading isn't necessary but removing spent blooms isn't harmful if you want to clean the plants.
Rockapulco impatiens are very easy to care for, provide them with a shady location, give them a bit of fertilizer and don't let them dry out too much and they will be happy campers. The shouldn't need to be trimmed back, but can be pruned to shape them at any time. If they get too tall, you can cut them back to promote additional branching and a more compact habit.