30% will shift the Long term fuel trims around 8%, any more than 15% LTFT's will pop a CEL for too high positive fuel trims. That'd be around 45% E or so if your trims are close to zero.
1:1 E85 and E10 93 is E47 and 99 octane. Requires around 16% more fueling though.
2:1 E10 93 and E85 is E35 and 97 octane, it'll need 10-11% more fuel. I wouldn't go more than that without a tune for it.
The LTFT's carry over to WOT as well but don't flog it right away until they adjust. Since E85 is 105 octane it'll raise your 93 to about 96 octane at 30% E. No more KR on a stock tune.
Here's a calculator.
http://www.intercepteft.com/calc.html
You really need the ability to log your fueling though.