I find KDE's config vomit overwhelming for my ADHD brain that just needs sane defaults.

Absolutely, this was the first thing that shocked me. Every single thing has the same top-level priority. If everything's important, nothing is. Everything is thrown at you simultaneously, "vomit" is an appropriate description.

but I'm unfortunately finding myself considering a Mac unless another opinionated DE like Gnome comes along.

Cosmic is definitely opinionated and looks like it's picking up the best parts of both KDE and Gnome. But it's still early in development.