There are definitely some tricks that you can play to quiet down an otherwise noisy SMPS, things that I have picked up in the course of a long career. Caging the beast is always a good start, as well as applying a grounded "belly band" of copper foil to reduce the racket radiated from the SMPS transformer.
Speaking of harvesting whale blubber, I'm working at melting away a bit of my own - perhaps not that hard dong power walks with 5lb wrist weights in the sweltering heat we're experiencing on the West coast (100F today). The blubber may be due to some overindulgence to the type of Vitamin B that's fizzy and comes in bottles...
Layout is a big factor in SMPS EMI/EMC problems in my experience of designing Functional Safety Industrial Control subsystems. I never did any high power SMPS, mostly below 10W, but they had to pass world wide agency approvals including TUV/SUD. EMI was always a hair pulling experience. EMC not so much. Although I have seen sensitivities up to 2GHz on some regulators that were layout/component value sensitive. Feedbnack loops need to be kept as short as possible to prevent noise pickup upsetting stability. Layout is a "Black Art".