Hello and thanks for posting!
For the benefit of any one else following this thread, the original question and my response are available here -> http://support.plugable.com/plugable/…
To your current question, the specifications for the power adapter for the dock itself do not necessarily reflect the power that is provided to the host system via the USB-C cable. To expand further…
The power adapter for the dock has to provide not only the necessary power to charge the host system, but also power the internal components of the dock itself. The USB-C Power Delivery standard defines different power profiles that can be provided to a host system, the most powerful of which our dock provides is 20V at 3A for a total of 60W of power to the host.
The Dell dock you mention supports similar standards, so that the Asus system did not charge when it was in use may speak to a host system incompatibility with 3rd-party docks (we can’t be sure though as we don’t have your model system in our lab).
The Asus Universal Dock (https://www.asus.com/Laptops-Accessor…) does not appear to provide power on its own, but rather makes us of ‘pass-through’ charging in conjunction with the original Asus power adapter.
Given your result with the Dell dock, I am afraid I would not recommend purchasing the Plugable dock for your system as I worry you might encounter similar results. Apologies if that sounds overly negative, but we like to do our best to set honest expectations up front to help prevent frustration later on.
Please let me know if you have any additional questions!