For the whipping cream, as long as you whip it to stiff peaks it should hold. Two hours should be nothing.
For the coulis, I would chop the strawberries in half so it would also be easier to blend. Normally a coulis is a puree. If you're not going to puree it then it will be more of a compote. And I would not soak the strawberries overnight. It's only sugar, strawberries, and water. If you're looking for a time saving step then that wouldn't be it. You'd be better off finishing the coulis a day ahead. Same thing with the mangoes.
"Boldness has genius, power, and magic in it."
Johann Wolfgang Von Goethe