Diffraction ordinarily gets to be more of a problem for a given aperture as you decrease the size of the format. The reason is simply that if the in camera image is smaller, you have to enlarge it more for the same size final print, so the Airy disk created by diffraction will be larger in that print.. It may get a bit more complicated than that for digital images because the size of the pixels may be comparable to that of the Airy disk. But in general you want to increase the size of the format if you want diffraction to be less of a problem, not decrease it.
I do some large format 4 x 5 photography, and diffraction is seldom a problem for me, I regularly use apertures such as f/32, which would be severely impacted by diffraction in 35 mm or smaller. My lenses often may be set as small as f/64. A 35 mm lens would never allow such a small aperture.
Leonard Evens Professor Emeritus, Department of Mathematics, Northwestern University