just want to draw a disk shaped particle and set size, color, & lifetime

Questions & Answers
1

All I need (for now) is something like DrawCircle(x,y,diameter,color,lifetime) for physics (2D) debugging purposes.
Unfortunately, all the examples I’ve found are for really fancy effects and I can’t figure out how to turn off all the advanced features of the Unity particle system object.

2

Sounds like you want gizmos or handles. Handles has Unity - Scripting API: Handles.Disc