Let’s not play here - 100% is not actually a magnified image, it is the native resolution. It‘s magnified only in relation to a display medium who cannot display, without magnification, the native resolution of an image.
For web display all these differences we are talking about are effectively moot - and 50 Mp or 100 Mp are meaningless. But, if you’re printing 1.60m / 1.20m or higher (I sometimes double that), for gallery viewing distances, then you end up with an image that goes way beyond 100% and that is indeed, a truly magnified image, relative to the native resolution of the sensor.
In this case , if you “pixel peep”, as in you evaluate an image at the limit of the natural resolution of the sensor (100% magnification) or beyond, you will most definitely find differences betweeen the various lenses, that may not show up at 50MP but will definitely show up at 100MP (same senzor size).
That’s why Rodenstock, for example, clearly states the pixel pitch (the pixel size in microns) for which it’s various lens lines have been designed / tested / optimized.
For my large prints, I always “pixel peep” between 200% and 400%. . For web display this could be indeed futile (cropping aside) .
And maybe restating the obvious: a 5k Imac screen will display a 14.7 MP unmagnified image, and that is not “web” display, that’s your living room display, going from that to web, will require further heavy compression of your image, mandated by the apps & websites you use for displaying your work. So, there is no 50MP or even 100 MP in that “unmagnified” image -oh, and your 50MP or 100 MP MF gear is definitely overkill if that’s your “final dimension” of display
Going back to the thread: only when viewing images at 100% and beyond, will there be meaningful IQ differences between the x2d and x1d, or between the 30xcd and 38v when both shot on an x2d.
Figure out what your final image display medium, dimensions and viewing distance are and then select gear & evaluate IQ accordingly.