Well maybe overthinking a little, but then reloading is serious business so can't' be too careful! Usually people crimp their bullets in the crimp groove unless there is some reason not to, like trying to make it longer to feed better in a rifle. And some bullets don't have crimp grooves. If your bullets do not push into the case of a loaded cartridge when you push hard on it, then it has enough crimp. As long as you are loading mid to low level on the charts, the amount of bullet seated in the case won't make much difference. And the shape of the bullets nose won't matter in a revolver.
As to brass cannelures, there are folks who have had brass case separations in their rifles, and the portion of the case that is stuck in the chamber is hard to get out. They say that the cases separate at the cannelure, and so some folks will not shoot that type of brass in their rifles. Most folks will never have that issue, but then it does happen. I've always used mixed brass and never had it happen, but last year I loaned my carbine to a guy for the last stage since his rifle broke. He was using his ammo and had a case separation. A friend and myself tried a number of suggested techniques, even using a dedicated tool for that, without success for a few hours before we finally were able to drive that piece of brass out of the chamber. So, these days I still shoot mixed brass, but if I am shooting all .38's I will try at the loading table to put the rounds with a cannelure into the pistols as much as possible.