Avatar Wan's story is really interesting. He was the first Avatar. In a world where the spirits and humans were more separated than ever, Wan was a bit of an outcast among humans. He learned to live among the spirits in the Spirit World, which was a very unusual thing at that time. Through his adventures there, he gained the ability to bend all four elements and became the first Avatar, uniting the human and spirit worlds in a way that had not been done before.
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.
Avatar Wan started as an outcast among humans. He entered the Spirit World, befriended spirits, mastered bending, and with Raava, became the Avatar, bridging the human - spirit divide.
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.