There are two things to consider when looking to reduce tire size. One is rim width, which you have noted as 24mm. The other is considering the geometry of the bike was designed around this tire size. Anything drastic will change how it handles and how high the bottom bracket is. This second piece makes more of a difference when talking mountain bikes, since on the road we are talking millimeters. 

With a 24mm rim, I would keep it at or above a 30mm tire. Going smaller than that would really stretch the tire and expose the sidewalls to more cuts. Cannondale also specs the Quick 3 (non CX) with a 30mm tire. The tire you reference above comes in a 32mm, which is a great option. That is the size I ride on my gravel bike when I have slicks on it and I love it. 

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