methanol is denatured too, and it's alcohol as well.
Denatured just means that its been rendered unfit for drinking.
The stuff sold as "denatured alcohol" is mostly ethanol and most of the time its denatured with methanol since ethanol is what is in alcoholic beverages.
Any alcohol can be used as a fuel.
Long story short, if you are going from ethanol to methanol, expect your AFRs to be leaner. You will have to increase the flow of alcohol or gasoline to compensate.
Methanol has a better latency of heat value (means it will cool your charge more) and has higher specific energy (will make more power when afrs are adjusted to match)