I honestly think that you are obsessing over it a bit too much, and over-thinking it. Ok, I'll confess, when it was time to make the transition for mine, my only concern was finding something that I found acceptable nutritionally, and that they would eat with gusto. I know, I know, the advice always is to transition slowly, and mix the two, and all that. But here's the thing... if you do that, you could easily end up in a situation where you've "transitioned" them to a food that they don't like, and only tolerated because it was mixed with something they did like. Then what have you accomplished? A cat that will only eat a certain adult food when it was mixed with a certain kitten food?
I advocate going to a store, getting a small quantity of a half dozen different foods that you think meet your nutritional standards, and then see what they like. If you find 2 or 3 different ones that they love, that's awesome. If only 1 or 2, oh well, that's a start. Then if you want to do a slow transition to them, go for it. Or throw caution to the wind, and deal with problems when/if they arise. Once you've established that you have a cat with a delicate stomach, ok, you can treat them differently, but most cats are pretty hardy imo. How would they even survive in the wild if their stomachs couldn't handle eating more than a single thing?