One unique feature is its comical art style that really brings the zany characters to life. The expressions and postures of the characters add to the overall humor.
Kazuma is one of the main characters. He is a typical NEET who gets transported to a fantasy world. He's not your typical hero, which makes him really interesting.
I'm not entirely sure, but it's very likely. TvTropes is a comprehensive database for all kinds of fictional works. Given Konosuba's popularity, especially in the anime and light novel world, it would make sense for there to be a section about its visual novel on TvTropes. You could check by searching for 'Konosuba visual novel' on the TvTropes website.
The Konosuba light novel is not a fanfic. It has its own unique plot, characters, and world-building developed by the author's imagination and creativity.