Not sure what mixing it would do. Naptha is normally a distillation of oil. I looked up the fraction. Light Naptha is 5-6 carbons so pretty close to white spirits and petrol. Heavy naptha is 6-15 so a bit less than kerosene IIRC.
Methanol is an alcohol. so completely different chemically.
I’m not sure what would happen if you mixed them, are they even miscible? Personally I wouldn’t as petrol (which is about 5-6 carbons) is not suitable for that type of stoves, it tends to explode rather than burn in a controlled manor. It all depends on the relative evaporation rates of the solvents and then that get’s really complicated.
If you were of an enquiring mind you could try mixing and see what happens. Start with low percentages and small volumes outside to see if you get an improvement. I doubt you would though.
Water is supposed to be beneficial to meths burners. Something like 5% addition.