External displays that have a native USB-C video input can be used in conjunction with the Plugable TBT4-HUB3C hub.  

However, in our experience helping others we have found that some portable USB-C displays may not work as expected when an external USB-C power source is connected to the display.

If your portable USB-C display has an external USB-C power source, please disconnect the external power source from the display when using the display in conjunction with the hub.  

The hub can provide up to 15W of power to the portable USB-C display, which will take the place of the external power source. 

An example of such a display would be the ViewSonic VG1655 display → https://www.viewsonic.com/us/vg1655.html   

A video that demonstrates the capabilities of this display is here → https://youtu.be/ferq4xz_A3M