CAD applications that are rudimentary translations of MS-DOS programs often operate quite slowly on the Macintosh, because rather than change their software to take advantage of built-in Macintosh graphics routines, they preserve their own, internal, "vector" method of displaying images. The QuickCAD board is designed specifically for those applications which use the vector method of graphics display.
Claris CAD does use the Macintosh toolbox, and therefore the speed improvement from a QuickCAD board does not seem to be significant. This applies to both Claris CAD 1.0 and 2.0.