If it's any help I run one with a 4090 and it's been brilliant. Certainly don't feel bottlenecked at all especially when dialling up the details on everything at 1440p 280hz.I'm mulling this exact upgrade at the minute, although with a 4080 I think I might be even more CPU bottlenecked than you. Glad to hear you noticed a difference. That's useful info, thank you.
Most of these benchmarks which you'll have seen will be running the 5800x3D with no PBO enhancement applied. The fact that you can put these chips pretty easily to -30 means when there's load (especially when gaming) you should get consistent max clocks at all times.
1% lows were noticeably better when I switched and that was only from a 5700x.