The 5800X3D was the first X3D chip released for the AM4 socket, later in it’s life, almost as an experiment. It was a huge hit and that’s why they’ve expanded upon that with the newer AM5 X3D CPUs (7000 series).
The 5700X3D and 5600X3D both came after the 5800X3D, and are both simply 5800X3D chips that did not pass quality-control, for different reasons.
In the case of the 5700X3D, all 8 cores are functional, but at least some of them cannot maintain adequate boost speeds. These were eventually rebranded as 5700X3D chips. The only difference between the 5700X3D and 5800X3D is that the 5700X3D has lower clock speeds, resulting in an effective 12% performance reduction in most cases (compared to the 5800X3D).
In the case of the 5600X3D, one or two cores were found to be defective. 2 cores are then disabled and it becomes a 6-core 5600X3D. However, the cores that were not defective are still able maintain essentially full speeds on each core (unlike the the cores on the 5700X3D). They knocked the speeds down ever so slightly anyway, but not to the same degree as with the 5700X3D.
So the cores on the 5600X3D are actually faster than the cores on the 5700X3D, and practically the same speed as the cores on the 5800X3D, but you only get 6 of them.
With the 5700X3D, you get all 8 cores, but with a ~12% speed reduction due to reduced clockspeeds.
So unless you actually need 8 cores, the 5600X3D will actually be faster than the 5700X3D in most cases.
5800X3D vs 5600X3D (notice almost identical performance at lower core utilization):
https://cpu.userbenchmark.com/Compare/AMD-Ryzen-7-5800X3D-vs-AMD-Ryzen-5-5600X3D/m1817839vsm2142471
5700X3D vs 5600X3D (notice how the 5600X3D spanks the 5700X3D in any task that isn’t fully utilizing all 8 cores):
https://cpu.userbenchmark.com/Compare/AMD-Ryzen-7-5700X3D-vs-AMD-Ryzen-5-5600X3D/m2280831vsm2142471
Below is a very informative article that covers many games (not WoW unfortunately). It includes the 5600x, 5600X3D, and 5800X3D, although it doesn’t have the 5700X3D. It shows how well the 5600X3D keeps up with the 5800X3D in basically all games.
Note how if you were to upgrade your 5600X to a 5800X (not giving you any extra cache, but giving you two extra cores), that would give you essentially zero performance increase for gaming.
https://www.techspot.com/review/2811-cpu-cache-vs-cores/
This picture in particular (it won’t let me post the picture directly):
https://www.techspot.com/articles-info/2811/bench/Average-p.webp
The thing is, that statement is completely incorrect.
WoW is one of the least multi-threaded games that is still commonly played.
There are substantial elements of the game that still only use one core.
Overall, WoW will spend most of it’s time using 1-3 cores.
Occasionally you will see it use up to 4 cores.
When the stars align, you might see it use slightly more than 4 cores for extremely brief periods of time.
So for all intents and purposes, WoW receives almost no benefit from anything past 4 cores. 6 cores minimum is ideal, not because WoW will actually use 6 cores, but because that gives you 2-3 extra cores to handle background tasks on top of what the game itself needs.
There will be no difference whatsoever between 6 and 8 cores in WoW, unless you commonly run CPU intensive tasks in the background while you game (beyond normal operating system background tasks and things like Discord).