RAM capacity barely affects power consumption

No, not in any way you’d notice.

The extra few watts from a second stick or higher-density module are swallowed by your CPU and GPU. We’re talking maybe 2–3 watts more under load, and that’s generous.

Even DDR5 modules use around 5–7W per stick at full bandwidth. Two sticks vs. four? Slightly more. But 16GB vs. 32GB in the same configuration? The difference is negligible.