1) Its trendy. I think it could potentially look dated, but I think the peplum silhouette works with a romantic/bombshell/retro personal style, so I think it also has the potential to simply look stylish well into the future.
2) You've identified one thing to look for yourself-- a more open neckline. I also look for the way the peplum falls-- some materials make weird folds, so watch for that. Another important thing is where the seam hits you-- try to get it to hit as close to your natural waist as possible!
3) I like 3 and 5. I think the material of 1 and 2 doesn't speak to me (looks too casual) and 4 is too baggy to my eye, and not in a cool way, but more in a messy way. I think 5 is the best for you in terms of a more open neckline.
Are you in Canada? If so, I recently got some really super cheap peplum tops from Urban Planet/Sirens. It would be a really, really cheap way to try the trend out. xD I don't think they have an online presence though. I've also seen some at Suzy Shier, also really cheap. And all the ones I've seen have deeper necklines!
In response to some other comments, I am short and have wide hips, and I feel like peplum silhouettes can highlight my small waist if I wear them right!