I've grown quite fond of the Mission Control way of thinking, but one thing annoys me.
When I use Cmd+tab to switch between applications
And then click down-arrow to see open instances of the app
Now when I use left and right arrow, a blue border surrounds each instance of the apps. Now when I click on an instance that's on the desktop that I'm currently on, that instance is shown. But if I choose an instance that's on another desktop, the application is "focused", as is the application name appears to the top left, but the instance is not focused.
I expect the focused desktop to change to wherever the instance that I focused is located.
I have quite a thick set of macOS defaults that I'm using, so I guess that there could be some setting there that messes up things.
In case you want to see my defaults, I have them public here.