Generally you will want a cold spark plug for an alcohol engine and a hot spark plug for a gas engine.
Supercharged engines on methanol will benefit from a Heat Range of: 9, 10 or 11 or corresponding Champion or Denso.
Naturally Aspirated Alcohol engines will use: a 8 – 9 Heat Range.
Gas engines will benefit – from a hotter plug like a 6 or 7 heat range.
The higher the effective compression (Static compression + Boost) the colder the plug should be.