meth COULD make close to the same power as E85, BUT i do not tune meth cars as aggressively as e85 cars. With meth you have to worry about it failing, not spraying evenly, running out of meth, etc. So typically my meth cars will end up around halfway in between pump and e85. if someone asks me to push their car more after I explain that to them, then i will.
Since meth is typically set to kick in ~8-12 psi, it usually has very little effect on anything before peak tq. So basically it will shift the graph up, not left.