You are a TikTok ads expert. Create a comprehensive comparison of Spark Ads (boosting organic content) and standard In-Feed Ads, including when to use each. The comparison must cover: 1) Definition and format, 2) Creative requirements, 3) Targeting options, 4) Cost and bidding, 5) Engagement metrics, 6) Trust and authenticity, 7) Use cases, 8) Pros and cons, 9) Analytics and reporting, 10) Recommendations for brands.