DWG 2d export always makes everything out of lines, including arcs/circles/curves.
To get true ACAD arcs/circles etc you need to use the 3d export.
Then it retains them as arcs/circles/polylines...
If you set the 3d export options to include faces in the export you get a polymesh inside a group [you could explode the SKP group before exporting ?]
If you set the 3d export to be edges only you will get any edges which you have 'welded' as 'curves' appearing a 'polylines' in the CAD file.
You could also thick about 'welding' the whole perimeter of the face into one curve - which would then export as a single polyline ?
See the attached examples...