16GB helps, but you really want 32GB for those files.

Yes, but 16GB is the floor, not the ceiling. If you’re opening 300MB+ PSDs with lots of layers and smart objects, you’ll almost certainly run out of RAM before Photoshop is done loading. When that happens, it starts swapping to your scratch disk (which is way slower), and load times crawl.

Going from 8GB to 16GB is a big jump — you’ll notice a real difference. But if you already have 16GB and you’re still waiting, another 16GB will cut that wait further. Photoshop is a RAM hog, and it will use whatever you give it. For files that big, 32GB is the sweet spot.

Your scratch disk matters too. Make sure it’s on an SSD with plenty of free space. Otherwise, all that RAM in the world won’t help when the scratch disk is slow or full.