Please read what methanol is and how it works. I don't care how much you think you know, refresh your memory on methanol.
You spray it after the maf, not only will the PCM see the IAT drop and add fuel but also it will take out timing too.
You can only run 50/50 or 60/40 mixture of water and methanol just because the pump can't handle over 60% methanol, it can but won't last.
If you have proper nozzles and filter that is meant for methanol than you won't have a problem.
And yes it can add a decent amount of power.
Do you gain hp/tq switching from 93 to 110 race gas. Yes as long as its tuned. Same thing for w/m