Your original theme choice is setup as fluid width. The center will change size depending on your browser. The two side columns stay at 200 px. Have looked at this one at 1024 wide to 1920 and it performs very well.

There are other themes that offer either a fixed or a fluid choice. Generally fluid is done for the center column. Thus text in the header at that location will be an issue if distortion is not desired. Or the design will have to take that into account.

Drupal, as you have noticed, has a lot of theme choices.

Have fun with the design.

Jim