Is 2x16GB better for overclocking stability than 4x8GB?

Yes, 2x16GB is better for overclocking stability. Fewer sticks mean less stress on the memory controller, reducing noise and improving the chance of hitting high frequencies or tight timings. This applies to both DDR4 and DDR5, even on high-end motherboards. If you need 32GB and care about maxing out RAM speed, go with 2x16GB.