I would assume your variations are based on Total Mechanical Timing
And at what RPM - I could see variations at much higher RPMs
Idle , probably nothing or you would notice a huge difference in Idle RPM
All the boxes I have tested , and i have a collection , didn’t see anything timing related say below 4500/5000 RPMs on a car
Would love to have a distributor machine
And 90% of the people on the street are shifting around 5,500 RPMs or less I would guess
I have had more issues with Ignition Coils failing at certain RPMs , or just failing all together then any ignition box honestly