Planning CTV Ads in West Coast Cities: Recommendations Needed

I'm interested in advertising on Connected TV in Los Angeles, San Francisco, Seattle, and Portland. I'm not sure where to start and would appreciate some guidance. I know that options include working with a Demand-Side Platform (DSP) that has access to streaming inventory like Hulu, Roku, and Paramount+. Another option might be collaborating with a direct representative. I'm less familiar with this direct rep method, so I'm curious if it's the same person who handles my linear TV buys or if I should reach out directly to the streaming services like Hulu and others. Any advice on the best approach would be very helpful.