I have sailed my C&C25mk2 for about 7 seasons. It is a great boat and has served me well. With an appropriate sail plan for the conditions, it comfortably settles into a 10-15 degrees of heel and with proper trimming and sail balance it will just about self steer as it settles into a groove. As stated by others, C&C's are genoa driven boats, although it happily sails with just a main. On the other hand, the other day I was feeling lazy and sailed on a 150 genoa (hank-on), with no main. The helm remained balanced, mostly on account of the large overlap and did not suffer from even a moderate amount of lee helm. (Winds were light, 5-7kts).
Generally speaking this boat is neither stiff, nor especially tender and settles into a groove pretty easily. It is truly a pleasure to sail.
My recommendation for a general purpose headsail (furler) would be a 130. In most conditions it will balance the main nicely and when the wind pipes up, reef the main and the headsail as needed to moderate your heel angle.