Are the YouTubers real?

Yes, all of them passed my verification process to make sure all data are real and not fake ones.

Is it safe?

This is not just safe! It's also very SEO friendly (backlinks from big channels) brings you unlimited traffic (once a video is uploaded, it stays there forever) and save you tons of money (you don't pay CPC for certain period of time buy a FIXED price)

What kind of links can I promote?

I'm trying to develop a good relationship with all YouTubers which means that they will be okay no matter what type of link (affiliate, eBay, Etsy, your video etc.) you will promote.