I apologise if I am wrong but it seems you were arguing against higher MP sensors on the basis of diffraction limitation happening at wider apertures which I presumed meant you had some knowledge of it.
Maybe it was my non-native english: diffraction limitation occurs only at small aperture diameters / large f-stop numbers.
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This seems to be saying that diffraction may not be an issue, but well capacity?
If this is a concern you have (which is fair enough) how would you get the information you need to make a buying decision?
Judging the technical IQ is at least a question if it is
comparable to the rest of the bunch now e.g. best APS-C cameras from Fuji or Sony who have very good sensors. IMO noise and missing detail can spoil IQ independently. Canons sensors show for my eyes/brain often a little bit more noise but also more detail while Fuji sensors have very low noise but fine details are on the mushy side. And if you check the noise in different colors (dpreview, itten color circles) I see some fine tuning for different sensors/CFAs - I think it has to do with the spectral width of the R, G and B filters which color exhibits more noise: A narrow filter spectrum reduces the amount of light which reaches the sensor but gives maybe cleaner final colors.
If a 32.5 MPix sensor shows a little bit more detail compared to the current 24 MPix sensor but has a little bit more noise I would judge both sensors as comparable. If the well capacity would be reduced significantly I would expect much more noise and judge the 24 MPix sensor as the better sensor.
I use dpreview, tdp, photonstophotos to check the scenes and diagrams to get some picture of the situation without splitting hairs.
At the moment I am very satisfied with M50 and 200D technical IQ while the 200D seems to have slightly smother transitions without being soft: I observed that the grip gets warm while taking photos, maybe they have the voltage conversion displaced in the larger grip far from the sensor which keeps the sensor cool and out of the stronger electromagnetic fields of modern voltage converters.
Just a chip layout as top view would not help to judge about well capacity ... if a chip producer finds a way to use the 3rd dimension to store charge well capacity could be increased by a large factor compared to current systems. The only drawback would be a decrease in ISO but having ISO 25 or 12.5 would be something like a no-cost ND filter replacement!
As you can see: my buying decisions are made between gut instincts and physics knowledge!