> In Gnome, can I move the UI elements to locations I want them in?

No.

> Or are we still in a situation where it's opinionated and you have to seek plugins to get an experience that you actually want?

Yes, 100%.

COSMIC feels like GNOME but done right to me. It's not as pretty but while it looks and works pretty much the same by default, you can choose what goes where.

Saying that, I still much prefer Xfce.