A sub-genre is a category within a genre (are not big enough to be a genre). Examples of subgenres would be Dark-comedy or Psychological-thriller. Positives to sub-genres are that they're easier to target when looking for a specific movie type and they are a more detailed way of describing a film. A hybrid genre is when two or more main genres are combined, for example: Rom-com or action and adventure. This would mean there would be a bigger audience therefore more chance of the film making money as there is wider interest. 

Seeing as we will be making a Thriller opening sequence it would make sense to list some examples of Sub genres of Thrillers so, below are some examples of Thriller sub genres :

Action Thriller
Conspiracy Thriller
Crime Thriller
Disaster Thriller
Forensic Thriller
Medical Thriller
Mystery Thriller
Political Thriller
Psychological Thriller
Religious Thriller
Romantic Thriller
Spy Thriller
Supernatural Thriller
Techno-Thriller