Below is a list of each of the targeting options for Video Ads:
1. Demographics – Choose age ranges, gender, or parental status
2. Keywords – Create a list of keywords to use for contextual targeting.
3. Placements – Choose YouTube channels or Videos that most fit your target market.
4. Remarketing – Use a remarketing list created from analytics, tagging your site from Adwords or a Video Remarketing list.
5. Display Topics – Choose "topics" for a broader matching than just a specific placement.
6. Display Interests – This is profile based. These are users that have shown "interest" in a topic. They may be on a "non-topic" video, but have been "profiled" as "interested" in your topic.
It's always a great idea to create multiple targeting groups (similar to the idea of an ad group) and test different targeting methods separately. Find out what works for you and generates the most views, longest view-throughs and conversions.