There really isn't a 'wrong' grip. You should try placing the pads of your finger wherever they need to be to help minimize wrist roll. It is very easy to roll your wrist over at the hit and having a grip that minimizes this will go a long way in having a smooth and controllable FH. I personally use a stack grip (pad of the middle finger half on the rim and on the flight plate.) For me, this helps to control OAT. A two finger power grip (both finger pads on the rim only) for others will help them control their OAT. Others, it might be a split finger control grip or just one finger. You should try them all and find the one that works for you the best.
The first thing I would work on is reducing OAT with mids or neutral fairway drivers with whatever grip gives you the best results. Once you have a smooth and relatively OAT free throw, then you can start experimenting with other grips to maximize your power. Resolving OAT problems at the start will go a long way to maximizing your distance. Having a solid FH before experimenting with power will benefit you much faster in the long run.
It should also be said to try and throw as flat as possible and get a level flight out of the disc instead of throwing with an anhyzer release to flex your drive out. A lot of people that usually do this for distance can't throw understable or slow discs well (I was one of these people). There is nothing quite like hearing someone say, "you just parked this 200' tunnel shot using a putter, with a flick?"
"Imagination is more important than knowledge" - Albert Einstein