Pros of self-inflating mats:
They are very comfortable, particularly in the larger sizes. They will also insulate you from the ground keeping you much warmer. If you do happen to get a hole in it, you will still be sleeping on foam rather than ending up completely on the ground.
Should you wear clothes in a sleeping bag?
It is best to wear a fresh and dry base in your sleeping bag to keep it cleaner and to keep you warm in chilly nights. These clothes should fit well, better if these fit loosely, so as to not cut off circulation, and to help trap heat closer to your body