Some time ago I played the demo of Sins of a Solar Empire. It's a space RTS game from Stardocks. It's quite complex and it take a couple of hours until one get enough familiar with everything to be able to play.
To help you, there's a a context info/help panel on the bottom right, that pops-up when the mouse is over an item. On the left side, starting at the top – there is an icon-list of all your assets. At the beginning I was quite often searching for a particular ship (like the 'builder' unit) in the icon-list on the top left while having the ship info, from the icon under my mouse, in the panel on the bottom right.
Now, the thing is, I've a 22" widescreen display and I noticed that it's quite a distance for the eyes to move. Doctors probably will love that as it's like eye-training … hehehehe
… but doing this often feels annoying. Actually one might even move the head too. Thus when searching for an item it's: move mouse to an icon, move eyes, read text, move eyes back, move mouse to the next item, move eyes back to the info panel … repeat until desired item was found.
In addition to that, typically in RTs games, you have the "build" menu section, usually at the bottom, and the amount of resources in your procession, usually at the top. It's not always like that but quite often and it's the same with 'Sins of a Solar Empire'. And the distance on my screen from bottom to top is also quite large. It's of course less the the diagonal but still significant. Thus when you want to check if you have enough resources to order/build the desired unit/component, you may wind up in the same procedure like described above for the info panel. Fortunately this has been solved quite well in this game. The info panel is right beside the build menu and not only it gives information about the unit but also the numbers of required resources will be displayed in red when the player has not enough of them.
So this is an interesting topic. Today application designers not only need to consider dual-screen setups but also the variety of sizes and aspect ratios.