If you're looking for more detailed audience data for creators on YouTube or Instagram you can invite them to your campaigns on Dovetale. 

Verified Data

Once a creator connects their account, you'll be able to view the audience metrics delivery directly from Instagram or YouTube as seen below for Instagram on the Audience tab in Dovetale.

Instagram Verified Audience - Instagram Insights allows Instagram Creator OR Business Account users to see analytics related to their profile and posts. Insights and metrics about an account include paid activity as well. Reach, accounts reached, impressions and impressions by day reflect both paid and organic activity.

Expanded view of the creator card: