Hi Charley,Atul,
Combustion in simple glow 2 strokes is very inefficient.
To make fuel mix changes and get the engine to reflect the change in its performance you would have to change the plug,crank timing and pipe timing to specifically suit the new mix.Not at all practical.So with 2 strokes we get the best compromise of prop/fuel/plug and pipe length for the particular 2 stroke we are dealing with.
4 strokes are more efficient.
YS 4 strokes are super at converting methanol and nitro into thrust,they just love that 30% fuel.
I don't know how much increase in nitro they can respond to positively as they have timing limitations also.
The critical ignition timing available from spark ignition means that the ignition timing can be fine tuned to suit fuel mix with the CDi, but only within the other timing/design limitations. To get deeper into this is interesting but imo thats for YS and Co.
For us users its enough to know the fuel mix range our particular engine is designed to work with.
Top fuel engines are designed for 90% nitro. A YS might not even start on that, I have not tried ,,,,, yet LOL.

Brian