For scale we're talking > 2TBps linear read and probably > 500MBps random 4k read in both cases, compared to on the order of 50-500MBps limit on the CPU side de

For scale we're talking > 2TBps linear read and probably > 500MBps random 4k read in both cases, compared to on the order of 50-500MBps limit on the CPU side depending on threading etc. So still CPU limited. If there's any problem with big file trees it's probably macOS's relatively slow filesystem so again, advantage to the faster CPU. It sounds like LightRoom startup is a little slower but if you use it for editing you're going to get that back in faster workflow. In general modern NVMe has removed disk as a significant bottleneck for normal peoples' workflows, even on Mac. That includes backups, zipping up collections of files, git compaction, etc. What scenario are you imagining here?