Catch22 - I'm not sure what it is you are seeking.
Based on the words you have used, I think you are really struggling with minutia in the tall weeds. Perhaps I'm wrong but I don't think I am.
Instead of worrying about: "soot", "heat staining ???" , "discoloration of the brass near the case mouth" and other obscure gremlins;......
maybe you should just concentrate on accurate loads that fall within acceptable pressure parameters and function well in your firearms?
I have reloaded and shot a LOT of 38 Special, 9mm Luger, 45 ACP and a lot of other cartridges in my lifetime. I have never really been consumed with concerns such as "soot" and "discoloration of brass".
So, just trying to be helpful here; My current standard 45 ACP load is a roughly a 200 grain LSWC with 5.2 grains of ww231. A lot of folks use 4 to 5 grains of Bullseye behind the same bullet.
My concern is centered on two factors: Is the load safe and does the load perform well.
I've never stressed about "soot", discoloration", "Does this spent casing clash with my shoes" or "what are the cool kids shooting".
You seem to be stuck in the tall weeds.