fwiw, toe-out on your front tires is a "stable" condition, while toe-in is an "un-stable" condition. i wouldn't try toe-in for the front unless you enjoy going slow. don't confuse more responsive with unstable. unstable means the car did something without you wanting it to. more responsive means the car did what you wanted it to do very quickly. drive a car with 1/4" rear toe-out on snow tires at 85mph if you want to know unstable. :shudder: i did once. won't do it again.
front toe-out, as i've posted before, can be thought of as dynamic ackerman. more toe-out and the car behaves like it has more positive ackerman, less toe-out and the car behaves like it has less positive ackerman/more negative ackerman. there is no "ideal" ackerman percentage, so you're looking at a best compromise situation. theoretically, a course with a lot of higher speed, large radius corneres would require a lower ackerman effect while a slower, tighter corner would require more ackerman effect. you would run less toe-out in the first case, a little more toe-out in the second. the difference is small though and you're better off just driving through it.
rear toe-out _is_ an unstable condition. it also has the effect of altering the vector angle that the tire will operate at it's max grip relative to the car. for example, we take a well setup car that is cornering at 1g. the inside rear tire is nearly completely unloaded, so we can ignore it's effect on handling dynamics. the outside rear is operating at a 12* slip angle. (the path the tire is following is turned to the outside of the turn 12*'s from the path the chassis is taking) if we add a little toe out, say -.05*, the tire has to still reach 12* of slip angle before it generates it's maximum force. to get to the point where the tire is operating at that slip angle the rear of the car has to "step out" wider then the front of the car. now the car is turned more for the same amount of steering input. best unwind the wheel a bit or you'll be waffling those inside cones!
*edit* cliff notes/short answer. no, toe-out does not reduce grip.