I’m a photographer currently still mainly editing on my 2014 27” iMac which I bought from new when it came out almost 8 years ago. It came with the standard 8mb ram, to which I immediately added two more 8mb chips for a total of 24mb. In all that time Activity Monitor has consistently informed me that I regularly use between 17-20mb of ram, and the activity graph is always in green. All this despite the advances over the years in my most used software Photoshop, Capture One and Nik software.
Knowing that I’ll upgrade this iMac in the coming months, probably with the Studio Max, I had been in two minds about the amount of ram I should get, but i have to say based on my own usage and experience over 8 years I agree with the posts above which say 32mb will be enough to see me through the next 5-8 years. Money saved on the ram upgrade will go towards upgrading the SSD to 2Tb, which I feel will be more beneficial to me. Have a look at ArtisRight on Youtube (linked in post above) for a wonderful overview and series of benchmarks of the Studio from a photographers point of view.