I'm sorry to say, in my experience the best CAD software
one can run on AmigaOS is MiniCAD for the classic macs...
http://macintoshgarden.org/apps/minicad-7It used to work brilliantly in Shapeshifter - better than
on any classic mac (ppc or 68k). The Amiga multitasks.
Unfortunately Basilisk on OS4 is unreliable and so MiniCAD
wont run in there.
OTOH, Shapeshifter still runs within OS4 UAE, but it's
a challenge to get in or out of the virtual Mac within the
virtual Amiga.
It would help if there was networking support in OS4 UAE.
Then one could just FTP in/out of the mac within.
Good luck,
PJS