To have example ps and lr run about smoothly together you should really get 32gb memory. I had before 16gb and it was a pain. Now i have 32gb and i have allowed nearly 300gb swap for both ps an lr and now it is decent. When i am working with astro stuff, mostly with milky way images, i allway work on the "final" tiff aka the one with lights and darks stacked on it. My comp is still quite old 8core amd, which is currently my bottle neck. But yeah 32gb-> is the memory you really should have.