Query:Differences in details of decoration between Veo-3.1-generate-preview and Veo-3.1-fast-preview

Which Veo model does Gemini use for paid plans, Veo 3.1 Fast or Veo 3.1? How is the Veo 3.1 Fast model different from Veo 3.1 in terms of quality? I know that veo 3.1 has better quality than veo 3.1 fast, but in what aspects? as “quality” is vast term. I am getting distorted ornamental designs in architecture with Veo 3.1 Fast; will Veo 3.1 make this result slightly better (note: I am not interested much in lighting or texture, but getting the arabesque designs right)?