Does dual-rank RAM make a big difference in gaming performance?

Not really. For most games, the difference between dual-rank and single-rank 32GB configurations is within the margin of error — maybe 1-3% at best, and you won’t feel it. Your GPU is usually the bottleneck, not your RAM, so focus on speed and latency like DDR5-6000 CL30 instead. Don’t pay extra or delay your build over dual-rank; your money is better spent on a faster GPU or better CPU cooler.