The untrimmed CAD export types (STEP/IGES) produce a standardized CAD file built from the native OpenVSP Bezier surfaces in the model. The surface resolution displayed in the workspace defined by Num U, Num W, clustering, etc. has no effect on the resulting CAD files. Once you have chosen a set of components and a format type, the Untrimmed STEP/IGES Options menu will appear. In this window, the desired length units must be defined along with a tolerance (accuracy) for the export. Multiple other options are available enabling users to tailor the export format toward their CAD program of choice. For example, some programs will import the model with gaps or breaks in wing trailing edges or fail to accept non-split surfaces. In these cases, options are provided to address these issues.
Unfortunately, the rules defining the STEP/IGES format are relatively loose and were defined by committee. This means that writing a STEP or IGES file is much easier than reading one. If your CAD program has issues reading an OpenVSP CAD export, try different options to see if you have some success. It may also help to write a STEP/IGES from the CAD program and compare or to research what specific style of STEP/IGES that CAD program expects.