Yes.
Can you clarify the question? Of course you can continue using files on the host. Or did you mean on the destination? It depends on your definition of usable: you can restore data from duplicacy backup.
Remeber, duplicacy is not a sync solution. It creates a versioned backup. Completely different thing for entirely different purpose. If you need sync — there are other solutions, like Resilio, syncthing, and various client side tools that allow data sync with optional encryption and mountability, like mountain duck with cryptomator, or rclone.
Or you can use both, it’s not mutually exclusive: sync for collaboration and replication and backup to maintain version history for disaster recovery and protection against mistakes and failures.