The book I linked to isn't so much a guide, but a short story collection. And you're definitely right, but like any genre, there are certainly tropes you'll find. When I started writing, I asked my editor if I was really writing bizarro, since I didn't write sex or gory violence (which to me, being new to the genre, seemed to be a must). But I was assured that even though those are common in bizarro stories, they're not a must, as not every fantasy book needs to have a dragon.
Defining bizarro isn't easy. The films of David Lynch, and Troma films like Toxic Avenger are pretty different, but they're both "bizarro" by some definition. Carlton Mellick III's crazy high concept stuff is bizarro, and so is Anderson Prunty's surreal, dreamlike lit fiction.
Like how Edgar Allen Poe and Cliver Barker are both "horror", but they couldn't be more dissimilar.
It's a lot of genre crossover in bizarro. Horror with comedy and absurdism, fantasy with film noir, surreal elements sprinkled in over whatever genre you're writing in.