When you set up a YouTube ad campaign, Google Ads has "Smart Campaigns," which helps newbies make the most of their campaigns via automation. By switching from Smart Mode to Expert Mode, you unlock the full capabilities of your ads. You'll have complete control over your budget, bidding strategy, etc. and it unlocks access to different types (Video, Search, App, Display, and Shopping).
Note: Once you switch to Expert Mode you can't revert back to Smart Mode.