But you usually don't shoot high FPS scenes at ISO 100. So you're loosing DR anyway, so that slightly reduced Bitrate should not translate to a real world disadvantage, right?
I not only sometimes shot action/sequences with 100 ISO, but my 7DII I have permanently set to highest framerate. When not shooting action/sequences, I'm usually bracketing where it too find it practical/best to shot at high framerate.
Unless you also set up a studio comparison with identical lighting conditions and settings to make your personal observations, any differences you see are hard to blame on the resolution differences.
As for white dots, that sounds odd. That's a type of noise I would expect for long exposures, or really hot conditions. As Michael pointed out, it may also be a technical difference.
I have 6 years experience with the 7DII. Never seen that kind of "dots" with my 7DII. I was shooting several sessions with the 90D over a couple of weeks, and the dots were consistent in high iso shots from all sessions. I don't need a studio-comparison on top of that to feel comfortable about making a conclusion for my kind of use. However as Michael points out, using other RAW conversion software than Adobe might make a difference. I don't know.
Anyway, as I see it, an R7 only makes sense if it can make the most out of long lenses. So it must have a sufficient pixel density to exceed the R5 and compete with the eventual R5's / R3 high MP FF body.
For me it's also a matter of price - and size+weight of normal and wideangle zooms. I'm never going to buy a camera priced like an R5, and don't want a bigger/heavier "casual/everyday kit" to carry around than I have now.