Well I voted for the first option but Ideally I would not just put them in one corner but rather a big patch of amazon swords or other plant of your intrest located in one area, not nesacarly the corner.
Either way just be creative and go nuts.
traditionally the most poopular method would to be to cover all along the back and the sides of the tank with plants.
...Just use you imagination on this one, you shouldnt be able to mess things up on this one
Some of the most fun I have setting up any tank is decorating it and making it an outlet for creative expression in your house. Just be creative and do whatever looks nice. Putting plants in there will provide cover but try to use your imagination cause it will make your whole experience better, and your fishes too!
I'm with Xenon on this one: I also really enjoy decorating a tank, making it look as good as possible, and also as enjoyable to the fish as possible.
I'd place the plants in both corners and against and near the back tank wall: this way, your fish have plenty hiding spaces around the edges of the tank, as well as enough free space to swim around in the middle and up front...
But like Xenon said, it's all a matter of personal preference (combined with a little common sense