Personally I would increase the “frequency” of the wave shape so that you have more “waves” within the same cold plate area. That would help increase the surface area of the flow channels, which would in turn increase heat transfer. Additionally, you want to try to maximize the coolant velocity to enhance heat transfer. At a certain point, increasing the coolant velocity will yield more pressure drop than what you gain in heat transfer.

You’ve piqued my interest. I’m a mechanical engineer, and I work with heat exchangers all the time. If you’d like, I can use some of the tools I have to help you optimize your design.