The 3d v-cache can still help at 4k, although the improvements are limited as it tends to be more GPU limited at those resolutions. Take a look at some example benchmarks between the 7950X3D and the normal 7950X - For example: https://www.anandtech.com/show/18747/the-amd-ryzen-9-7950x3d-review-amd-s-fastest-gaming-processor/10
If the CPU is mainly for FM purposes, how about going for the standard 7950X, 7900X (non-3D v-cache), or even a cheaper, more efficient 7900 (non-X)? From the benchmarks so far you wouldn't be giving up much performance in FM, you would save money, and still have a nice upgrade path in the future. Obviously this would depend on what CPUs Cyberpower offer (I always build my own so don't look at pre-build options).
If FM is your main use of CPU, the ability to upgrade in 2-3 years would be nice from a FM perspective and is something that you won't be able to do with Intel. Any upgrade you make now will be a massive improvement over what you have already.
I'm not an AMD fan-boy or anything. I just think that with FM being CPU intensive, having a cheaper upgrade path in a few years would be a good option when newer/faster CPUs are released, compared to Intel where you would need a completely new motherboard and CPU.