The CL primary timing has very little direct perf changes. The other primary timings have some slight perf changes but not by a whole lot.

The main perf differences will come from secondary/tertiary timings which will be auto trained by the motherboard (or set manually of the BIOS supports manual tuning). CL has some influence on certain timings but the differences are still minor for what will be auto trained. The timings set by the auto training will be dependent on the memory IC type, binning of the IC, PCB quality of the DIMMs, voltage being supplied to the DIMMs, DRAM frequency, CPU (IMC [integrated memory controller], some other misc stuff), and slightly by the primary timings.

The XMP values tend to allow one to infer what IC is being used and the bin of it (if said IC is even binned), which is what usually tends to make the biggest differences in what the timings will be. But the advertised primary timings themselves tend not to be the reason for perf differences. Note that better XMP values won’t always mean a better DIMM. Possible to have high quality ICs in a low tiered product.