SC1 is softer than the SC2. I usually go Sc2 because they last longer and are not temp sensitive as the SC1. The SC1 does grip better, but only for a day. If its really hot out, I go SC1.
You can mix and match. It all depends on your akill level and how you manage the tires. Try the SC2 front and rear and see how it works for and go from there.