Generally, the optimal f-stop roughly correlates to image size (among other things, the most important being lens quality) ... but not to pixel count or pixel pitch.
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I think you are right that the resolution of the sensor (including film as a type of sensor) does not affect the f-stop at which resolution is optimal. That still leaves the question of how much resolution one gets at that optimal f-stop, or at any specified f-stop, where we agree that sensor resolution is relevant.
When DOF needs come into play, the optimal choice of f-stop can be considerably smaller than the values you talk about, which are based on optimizing the sharpness of images of subjects lying at the focal distance, ignoring OOF effects for subjects at other distances.
However, when one stops down for greater DOF, sensor resolution becomes even less significant in overall resolution, with diffraction and OOF effects becoming the main considerations at small enough apertures.
The main connection to sensor resolution is that, if a given aperture is chosen on the basis of best handling aberrations, diffraction and OOF effects, there is a resolution limit, no better than that due to diffraction alone, which means that increasing sensor resolution too much beyond diffraction based resolution has little benefit for overall resolution. My 1.4*N to 2*N estimate is thus mostly a guideline for that "maximum useful sensor resolution at a given aperture ratio."
For example, landscapes are one of the dominant examples of the most extreme resolution needs, and typically have DOF needs leading to use of apertures f/8, f/11 or smaller with 35mm. At such apertures, there is little benefit to reducing photo-site size much below about 4 to 5.6 microns, or about 27 to 54MP.
But it gets worse: when one wants to make use of new higher resolution of sensors 16MP and up, seeing that resolution requires a combination of larger prints and closer viewing than with lower resolution images, which makes OOF effects more noticeable, so that adequate sharpness across the desired DOF will tend to push the needed f-stop higher. Once one needs about f/14 or higher, for adequate DOF in the desired "big, closely viewed prints", diffraction and other effects limit useful pixel counts to about that 16MP.
Since landscapes are almost the dominant example of photography that can benefit from high pixel counts, this makes me wonder how much use there will be for pixel counts significantly higher that 16MP. (Larger sensors do not change these DOF/diffraction based limits on useful pixel counts at all, since higher f-stops are needed for equal DOF with the larger focal lengths of a larger format increasing the diffraction spot size in proportion to focal length).
I wonder how the artistic effect of landscapes and such is changed by the step from 16 or 22 up to 31 or 39 MP. I do not mean "print peeping" comparisons showing greater sharpness at the focal plane when using the same aperture with a higher pixel count, but the overall artistic impression, including more noticeable OOF effects when one looks closely enough to see that extra sharpness. Maybe it still works because
1. "Overall viewing", from far enough away to see the whole image, looks at least as sharp with fewer pixels, and probably with as much DOF.
2. Closer scrutiny shows some parts of the scene at least with more sharpness and detail, even though this benefit is limited to subjects only within a part of the "overall in-focus range".
And I suppose that other specialties like architectural images often benefit from high resolution without very much DOF.