This is like just souping up a 54' Chevrolet Bel Air. It's fast but it is still just old tech.
Wow 5% for the extra $300... money well spent there. Also why would you get a 3950X for gaming? I mean we could bring up workstation tasks between the 9900K and the 3950X see how the 5.5% looks there.I stopped hanging heavy air coolers bending my motherboard, blocking memory slots and blowing hot air around in my case ten years ago. My PSU, CPU AIO and GPU all have fans that operate only as dictated by set temperature curves. In casual usage like internet they are quite and idle. When running at overclocked speeds they are still quiet and rarely run at anything approaching fan max. . There are no case fans.
Read the chart in the gaming reviews. For 50 top Steam games Intel outperformed AMD's best by 5.5%. Intel's top chips also beats AMD in MS Office. The top system for a 9900k cost 7.5% less than AMD's 3950x best.
https://www.legitreviews.com/best-cpu-for-gaming-top-50-steam-games-benchmarked_218261/4