Lowest resolution does not always yield higher frame rate. Most cards are made to run at high resolutions. I don't mean all are meant to run in 1600x1200, and this only applys to some, but just so you know.
In my case playing in 640x480 doesn't help me out
But anyhow, there are many mods out there, in seperate pieces that you can easily throw together to make a nice less-space-taking UI.
Most of my Mods cut down on screen space taken up.