Michael De Lazzer wrote:...bought a used 2019 Mac Pro...16-core processor (32 threads) 96Gb RAM, 4Tb, Radeon 580x...I will likely expand the RAM and add the Afterburner card since I cut exclusively in ProRes...What is a great video card setup for this Mac for Resolve and After Effects?...
Afterburner only accelerates *decode* of ProRes and ProRes RAW. It does nothing for encode, render or anything else. Resolve does not support ProRes RAW, so AB would be only for ProRes decoding in your case, which does not need hardware acceleration -- it is already optimized media.
Re an improved GPU, yes that would help, especially for Resolve. The 580x is OK but not really fast. I recollect some tests showing varying efficiency of GPUs being utilized on the 2019 Mac Pro, but I don't remember the specifics.
I wouldn't just buy an expensive GPU based on synthetic benchmarks. You want reviewers who used application benchmarks with various GPUs in the 2019 Mac Pro, focusing on the software and workloads you use.
If you do work in Fusion, you want to see various Mac Pro benchmarks or user feedback using that. If you use largely After Effects, you could probably get better advice on a forum for that.