Vondy gives you generous credits to try out the generator as well as the full library. For generations beyond the free tier, Vondy has a pro subscription and usage-based plans.

How long does it take?

Depends on the model you pick. Better models often take longer to generate. For images, it can range from a few seconds for a quick draft to a few minutes for a higher quality polished generation.

What genres work best?

Thriller, romance, fantasy and sci-fi are the easiest since those genres have a really recognizable look. Niche subgenres can work but you might have to describe what you want more specifically.