The thing to keep in mind is that strawberries are sweet, and the sweetness will not be there from the strawberries because all those sugars will ferment out. So, if you want that sweetness you'll have to add lactose or something.
As to how much to use...I use 4 lbs of strawberries in my strawberry blonde (5 gallon batch IIRC), which has won a couple gold medals in competition and people seem to like it. However, some people like even more strawberry character than what is there, while some people say it has the most strawberry character of any strawberry beer they've tried. I think it is one of those things that varies by individual. IMO it has a quite strong strawberry aroma, but the flavor is a bit more subdued. If I were doing this in a wheat beer I might add a bit more than 4 lbs because the fruit will compete a bit with the wheat character.