I recently built an UNRAID machine using a 3900x (12c/24t). I have 7c/14t dedictacated to my gaming VM, and the other 5c/10t for Plex, Unraid, a linux VM, and all the dockers I have running. 5c is more than enough for my plex and linux vm and other dockers. Add another 2c/4t for minecraft and youre at 7 or 8 cores for the machine, leaving a full 8 cores for the VM if you'd like. That's all up to you and can be tweaked as needed. I'm confident the amount of power in the 3950x will be good for you, and I don't think the vastly more expensive threadripper will be worth the money for your use case.
PCI-E lanes are dependent on the SSD. You have 2-lane and 4-lane variants.
Take this with a grain of salt because I learned this recently, it might not be correct. If someone could confirm or deny that would be appreciated:
Without threadripper, the most PCIE lanes you're gonna get is 24. That's 16+4+4, which means a set of 16x, a set of 4x, and another 4x for the chipset, which will take it's 4 lanes and divide them up for you as needed. So you can definitely use all your devices, but they might end up sharing lanes. Unless you're fully saturating all devices all the time, this really isn't a problem for most people. I do not know your specific use case though. Why 3 nvme drives? Can you increase capacity and reduce the number of drives?
Also, I am fairly sure the GPU will not exceed x8 lanes. With PCIE 4.0 your speed per lane is essentially doubled, so an x16 card at 3.0 will be an x8 card at 4.0. Again, not sure if this is 100% accurate.
Make sure to download the tips and tweaks plugin - it helps enable the full turboboost on the CPU.