[ese8413]

Do Neos actually breed that fast? I have no idea what I would do if they overpopulate.

They can, I wouldn't worry too much about overpopulation. From what i've experienced and from chatting with others, they tend to balance themselves out.

So, are they actually that hard? What are your arguments for and/or against shrimp?

I think its only as hard as you make it. If you're willing to learn about water chemistry you'll definitely have a better experience.