Hmm ok, maybe I'm confused. If you run a campaign mission, the same mission, and fly it (you are technically "in-flight") Test your settings etc. Then restart the same mission, and test out settings again and so on. It serves the purpose of stress testing your rig & settings because the campaign missions can be very stressful on your machine.
Most campaign missions have a lot of units and action going on, so fly the mission and test settings. Adjust settings and fly again..etc. That's how I did it.