FWIW, wanted to let you know that I successfully connected my 2016 13" MBP to the 5K Dell 27" UP2715K display. This is basically the same panel that is in the Retina iMac. 27": 5120 x 2880 @ 60Hz. Though the official Apple page says that the 2016 MacBook Pro is not compatible with this display, it is wrong. I tried many combinations of adapters and cables until I found one (and only one) that works. You need two https://www.amazon.com/gp/product/B018AX3HJO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 Club3D USB 3.1 Type C to DisplayPort 1.2 UHD adapters, and two full size (not mini) DisplayPort male to male cables. This setup takes two of your four USB-C ports (doesn't matter which two) and will give you full 5012 x 2880 60Hz seamlessly + your laptop display even on the 13" Iris graphics, without having to wait for the LG display. Truly it looks like I'm sitting in front of the Retina iMac in terms of the panel.