

I think that depending on budget, 32GB to 64GB is a good place to be. The reason I chose 32GB unified memory is because Lightroom Classic works better if it has at least 12GB for itself, and after adding what macOS wants, and how much memory you want the GPU to be able to take from unified memory, 16GB seemed a little tight, especially if you then want to open another application such as Photoshop. Lightroom Classic and Photoshop run smoothly, and the most telling thing is that compared to my previous Mac, a quad-core i5 MacBook Pro, with the M1 Pro the responsiveness of the Spot Removal tool is getting close to reasonable! I wasn’t aiming for the most powerful, but the best balance between cost, performance, and portability. I use the lowest base CPU (8-core) 14" M1 Pro with 32GB RAM, and I am very happy with this choice. You might want to look at the similar, longer discussion already in progress on this forum:
