Stopped reading when you said Mac OS 9 was slow. Compared to the current Mac OS on modern hardware, OS 9 was blazing fast even on that old hardware. Most things being single threaded also meant that even if your machine was lagging, you could queue a bunch of keystrokes and clicks and they’d all execute in perfect order exactly as expected as soon as the lag stopped. Nowadays all those keystrokes and clicks just fucking vanish.