Ask HN: Where is the border between allowed and disallowed in Apple appstore?

I was thinking about building an app for adult p2p video calls with random people similar to chatroulette but with its own unique (as I hope) features.

I was absolutely sure the app I'd have built could never be approved in App Store because they don't allow adult-content oriented apps to be published.

So, that's fine, I knew it from the start so I started building a webapp optimized for mobile devices as the primary goal. But, when I had a look at the potential competitors, I found out some of them have their apps in App Store looking absolutely fine, searchable and installed by hundreds of users. Though, the apps have these words or similar in the descriptions: "Dating app", "Meet new people", "Video chat with girls" and so on. They don't have any clear signs they expose any adult content, but in practice obviously it's their purpose.

Ok, that's fine as well, I am not here to blame anyone doing their business their way. But my concern is also practical - seeing these apps to be safe and sound in the AppStore, what if I consider to build an iOS version of my webapp and publish it?

What would be the symptoms I am getting into the yellow or red zone for the AppStore reviewers? I know I can pretend the video app I am building is just for nice innocent flirt and smiles.

But how the AppStore reviewers see it? I am sure they saw millions of shady apps they precisely know the purpose of.

Are there any guidelines for such apps to not fall into the blacklist?