You are not going to have to overclock a 5800X3D. I’ve been running MFS with a 5800X and an RTX 3080 on ultra settings, except for LOD and traffic where I exercise just a little restraint, and the rig is never CPU bound. And I air cool the CPU with a Noctua NH-U12A. I think that your choice of an Arctic Liquid Freezer is correct, but a 420 is massive overkill. I truly believe that an Arctic 280 or even a 240 will cover the 5800X3D in MFS just fine.
You might want to take a look at this thread and follow the posts by Grabber523. You want high-end hardware for MFS if you can afford it, but, like he says, you can run this sim on a potato if you adjust the graphic settings optimally.