You can generally charge out from the Charge 80/40/20 at the same time as charging in via USB-C, though there may be combinations of devices where it does not always function. The pass-through functionality works best with a stable supply.
If you're looking for consistent, reliable pass-through charging with a specific device or set of devices, we'd be happy to talk through specific use cases with you to determine whether the Charge 20/40/80 will work to pass-through charge to your desired device without issue.