9800X3D is supposed to have Eco mode with a lower TDP cap, similarly to other AMD processors. I don't see it included in the initial reviews, but it would be curious to see the followup data. If the history is anything to go by, it would significantly decrease the power consumption with only a marginal performance impact.
I have the 7950x, and if I set it to 65W eco mode, I still have basically the same geekbench score
65W: https://browser.geekbench.com/v6/cpu/6126001
105W: https://browser.geekbench.com/v6/cpu/5821065
I actually haven't tested it with 170W (which is the default for the 7950x) for whatever reason, but the average 7950x score on geekbench is basically the same as my geekbench scores with lower than normal TDP.
https://browser.geekbench.com/processors/amd-ryzen-9-7950x
I wouldn't be surprised if the same is possible with the newer CPUs.
Nice added bonus is that my PC fans barely spin (not at audible speeds)
my 2700 is due for a refresh next year, so that's what I plan to do, get one of these fancy X3D versions, then cap it to hopefully sub 100W