Can anyone tell me how to get arc and circles from Rhino’s Make2D command into into AutoCAD and have them remain as arcs and circles? They always come in as teeny line segments using R12 Lines & Arcs as the export settings.
Using the Default settings they import as AutoCAD splines (a curse if ever there was one!)

AFAIK, the Make2D command creates drawings based on projections onto the CPlane. Not sure if it is possible in Rhino, but it definitely is possible to segregate the segments based on the input geometry using the VisibleIndex output.

For Rhino, try Join command to reduce the number of objects (without deleting them), and then use SimplifyCrv to remove unnecessary points. It works most of the times.

Try saving as .dwg - 2007 Natural Scheme.
Arc’s and circles will be arc’s circles in autocad.

If the rhino drawing is curves neither arc’s or circles then they will come across as splines.
In this case convert curves to arcs in rhino, the converted arc’s won’t be exactly the same as the curves, so you will need to adjust to where you are happy with.

You might want to try running simplify on the curves first. Circles and arcs seem to be NURBS circles\arcs and probably export as splines. Simplify will convert to simple arcs circles.