I would limit the drawing to get the maximum speed out of it. You need to see how many microseconds per pixel you can get it to perform to. ( eg horizontal = time, vertical = amplitude )

So see if QuickDraw will run fast enough, I suggest something like patXor and LineTo as the main calls.

If not you may have to drive the screen buffer yourself.

Stick to original monochrome Quickdraw, not colour.