I am now using a very nice 2016 MacBook Pro 15 inch with two 4K external screens and two 1920x1200 displays. It works quite well, especially the 4K screens.

I am still using the DisplayLink USB 2.0 hub/video thing to drive the 1920x1200 screens as there is not yet a USB-C or Thunderbolt 3 powered hub available that fits my requirements.

Turns out that virtually all the existing USB-C charging hubs are not compatible with the 80+ watt power requirement of the 15" MacBook Pro charging, they were spec'ed for the lightweight MacBook or the 13" MacBook Pro, both of which need 60 watts or less. Even the Apple USB-C Digital AV Multiport Adapter (Apple USB-C to USB-A charging adapter) is not rated for the full 85 watts.

Which means one of my USB-C ports must be dedicated to charging the laptop from the OEM Apple charger. Two USB-C ports feed the dual 4K screens, leaving one port for everything else, via that DisplayLink unit. I expect in a few months these troubles will be resolved as more and better hub products arrive,

In the meantime, articles such as this from the wirecutter will attempt to clarify, explain and rate the panoply of USB-C cables and adapters bubbling into the marketplace.