YouTube Ad placement for best ROI

I am looking for an experienced creative person who is an expert at YouTube ad placement. I have short ad videos which I want placed on YT videos of similar content for "Look Alike Audiences" also known as shared audience marketing. These short ads will be placed on long form YT videos of the highest, most popular videos. People searching specific topics will be shown the most popular YT videos and will have to view my short ads before viewing the longer main video. I would like to see examples of your work.