I Have an Optiplex Precision 360 mini tower, and want to upgrade the RAM. My processor is the Intel i9-9900K, 3.6GHz cpu, 8 cores. The current memory is 2x oem DDR4 8GB sticks @2666MHz.

There are now many more versions of these chips than when the computer was assembled.  Is there any advantage to picking a DDR4 chip with higher clock speed, or is the memory speed limited by the motherboard?  Or are there downsides to running faster RAM on this computer?