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.
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.
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.
Ichigo's Soul Reaper powers are based on spiritual energy, and Korra's bending is based on her connection to the elements. Their powers could interact in a way that creates a new form of energy. For example, when Ichigo uses his Getsuga Tenshou near Korra while she's bending, it might create a shockwave that combines the force of the spiritual energy blast with the element she's bending. This could be a very powerful and unique combination that they could use to defeat enemies.