Well, without more details it's hard to fully tell this story. But generally, in the Avatar world where Korra exists, if there's a story about Noatak being a 'pretty boy' in relation to Korra, it might involve their interactions, perhaps some kind of relationship development, either friendly or something more complex. Maybe it's about how Noatak's appearance and his actions towards Korra play a role in a certain plot within a fan - fiction or a less - known arc of the Avatar lore.
Perhaps it's a story of rivalry. Noatak, with his charm as the 'pretty boy', is in competition with Korra for something, like power or influence in their world. They constantly try to outdo each other, and their interactions are colored by Noatak's good looks which Korra may find both alluring and annoying at the same time.
The Legend of Korra comics are definitely worth a read. They capture the essence of the franchise and bring fresh perspectives. The quality of the storytelling and the visuals make them a great addition to the series.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
To be honest, I don't have an exact figure. But you can look up on popular comic book databases or ask in comic book enthusiast communities to get a clear idea of how many The Legend of Korra comics are out there.