It doesn't make more air go into the turbo so no doesn't bring it on earlier.
Does let you play with timing which can result in some midrange and top end changes
Wouldn't expect it to spool faster though.
Water meth is explained a lot and so is e85
They are both pretty much on par.
So it's just up to what you feel like doing.
One thing I guess you could say is if the meth fails for any reason you can do some damage.
But e85 is safer in that regard.