What GPU features are most important to LR DeNoise?

This is probably the best place to post that question, or at least I can’t think of another sub-community that would be more appropriate.

The problem with the delay in responses is that probably not a lot of users understand Denoise at that level. Which means that for an answer you can count on, you’ll probably be waiting for someone knowledgeable from Adobe to answer. Actual engineers are known to pop in from time to time and answer questions, but that isn’t guaranteed because technically this is a user forum, not a direct line to engineering. 

As an example of the limited detail users might know about this, I’m about to tell you everything I know about Denoise and GPUs.

On PCs, people have the most luck with the latest greatest Nvidia graphics cards, like the 40x0 series. But you already know that. I think Tensor Cores are the most important component for Denoise but someone else will have to confirm that. I also don’t know if Lightroom Classic can use any of the NPUs available for PCs.

On Macs, what matters most is the number of GPU cores because Denoise performance scales linearly with those; doubling the GPU cores usually halves the Denoise time. If Adobe can re-enable support for the Apple Neural Engine NPU, Denoise time should drop by an additional amount as it used to before Adobe disabled support for it due to issues.

On both, GPU memory is not really an enabler, just a potential bottleneck if there isn’t enough. In other words, once you have enough graphics memory to do Denoise properly, adding more won’t speed it up much further. How much is a good amount? I’m not sure but I’ll guess 6–8GB and after that is diminishing returns.