The fans you followed through Supercreator will remain followed; cancelling doesn't undo anything the Auto-Follower did on your OnlyFans account.
More broadly, everything that lives on OnlyFans itself (follows, sent messages, sales) stays exactly as it is.
What you lose access to is Supercreator's tooling: Izzy stops chatting, analytics stop updating, and CRM data, saved messages, and Izzy's configuration are no longer accessible on the platform after your subscription ends.