You can set any resolution you like, using the PRESET or RESOLUTION fields in the export box.
Those that offer "widescreen" provide two choices: letterbox or crop and zoom.
Here, a project sourced with a 4:3 and a 16:9 video was exported in both modes at 167x130. Aspect ratios looked fine.
The 16:9 image is shown letterboxed on the left. It's cropped/zoomed on the right, at the loss of some content - which may what you want.
Of course, an image/video can be manipulated via SCALE and other effects prior to export, to achieve the desired result.
