OP, a coil is a electrical transformer, there are two types of transformer, step up and step down.
Ignition coils are step up and they will only make the amount voltage needed to jump to the least resistance path to ground, which can be the spark plug ground strap or out to another easier path to ground.
On your deal using a ECU doesn't the ECU control the voltage to the positive side of the coil connectors ?
Or does it pulse the negative ground side
Either way you have seen a noticeable difference between the two ballast resistors, correct
One or input two volts difference will not burn up that coil
I know guys that ran that incorrect Accel Super coil on the early MSD race gold boxes, those boxes step up the input voltage to the coil to over 200 Volts D.C. to make them charge quicker so they could multi spark to the plugs
I found out later that those boxes needed the Mallory coil # 28880 ( I think that is the correct pt. #
) which had less primary winding ratio than a conventional coil did which help it recover and reach max voltage output quicker so it would multi spark better
Lots of choices and paths of information to help you make the best decision
Don't get lost in the details, if it ain't broken, don't fix it
The more you learn the more you find out what more you need to learn
Good luck