I’m no AMD expert, but I did just switch from Intel to the 5800x3d. The 1:1 memory ratio is between that and the infinity fabric, which I don’t think is the same as the raw core clock speed. I did see references to how it maintains that ratio up to 3600 MHz when I looked into a manual OC of my memory. If using memory running beyond that, the ratio changes, but I don’t know enough to explain how or why.
To @Nitoxium I think part of your issue in picking parts is a result of dealing with a system integrator that limits you to selected pre-set part combinations. For example, you should be able to run 3600 MHz ram with the 5800x3d with no problem, but likely that specific SI doesn’t offer that combination for whatever reason. I’ll also address your other parts question.
If you get the 3080 gpu, there are two versions. The original version is 10 GB, but the newer version is 12 GB and has more processing power. I would try to get the 12 GB version if at all possible, but is not as common. Check some YouTube videos to compare and see if the performance trade-off of the 10 GB version is worth it to you.
Back to your original question on cooling, the 5800x3d doesn’t appear to need a ton of cooling, even at a full core workload. In benchmarking mine with a Be Quiet Pure Rock 2 (their mid level tower cooler) in their 500fx case, and an all core -30 PBO offset, I could maintain full clock speeds at 72° C, and it doesn’t start to thermally throttle until about 80°C. When playing MSFS, temps are in the mid to low 60’s since the load is much less. An AIO would be cooler still, but may be overkill and a waste of money unless you are looking at buying parts for the long term or in a hot environment.