How it works
Memory timings specify delays, measured in clock cycles, for particular RAM operations. CAS latency is one timing within a larger set. A lower CL number does not automatically identify the fastest memory because the duration of a cycle also depends on the operating clock. Comparing kits therefore requires both data rate and timings, plus the platform's supported configuration. Capacity is a separate question from latency.
Published performance profiles can differ from the conservative settings the system uses initially. Enabling a supported profile may change frequency, timings and voltage together; it is not simply removing a software speed limit. The memory controller, board, firmware and module combination affect stability. A kit stable on one system can behave differently on another. Practical gains also depend on whether the workload is sensitive to memory latency or bandwidth.
Practical checks
Record current settings and confirm compatible modules in the manufacturer's documentation. Distinguish advertised kit specifications from values actually applied by the system. If a supported profile is enabled, test memory and the relevant workload and watch for crashes or corrupted results. Restore the known working settings if reliability changes. Do not combine arbitrary timing numbers from unrelated kits or increase voltage without understanding supported limits and the platform's procedure.