Short answer: both work. Spaceback builds creatives from organic posts and from social ads (dark posts / sponsored posts) alike.
Organic posts
Anything published on the brand's public profiles imports directly — connect the handle or paste the post URL.
Dark / sponsored posts
A dark post is an ad that never appeared on the profile feed. Fully supported:
Meta (Facebook/Instagram) — connect the brand's Meta Ads handle and use Browse ads to pick straight from the ad library.
Other networks — paste the ad's post URL on the Import page.
About the engagement counters
The counters shown on your ad unit reflect the source post at import time and stay current while the post remains synced — organic posts usually carry the social proof that makes these units perform.
Tip: not sure which post to pick? Social Intelligence ranks your library — Trending now, Most engaging, Hidden gems — so you don't have to guess.