What is the best social media platform to run campaigns on ?

There is no definite answer to this. As this is a case-by-case basis, that is to be determined between the Brand and the Creator based on campaign goals and specifics. The majority of branded campaigns are executed through Instagram, followed closely by Tiktok, then YouTube, Twitter, and Facebook. 

If a Brand wants to work with you in order to promote a new clothing item for a fashion line, it may be best to post on Instagram for that portion of the campaign. If the Brand would like you to showcase their product while incorporating dancing, audio, and visuals in the form of a video then TikTok may be the place to go. If you have a big following on YouTube and the Brand wants you to talk about their product / service for 15 seconds and describe your experience with it, a shoutout in a YouTube video would fit perfectly for that! Remember, every campaign is different and each Creator excels differently in the social media marketing industry.