just wanted to share some info regarding this. I have a 15" late 2016 MBP (the one with the four USB-C connectors running TB3), I am running this on an LG 38" screen with 3840x1600. On medium settings, I got around 22fps in that scenario. I decided to go with an eGPU and give that a try. So I got me a Sonnet Puck 570. Here is what I can say so far:
1. Support is seamless, there is nothing you can do, and nothing you have to. Plug it in, and go. From what I can tell, it will replace the internal fast graphics of the MBP, so the automatic switching is still there. The TB3 cable is included with the Puck.
2. If you are using the Puck with an external monitor, the Puck has to be in between. It will accelerate the internal display if you just connect it to the MBP, but if you want an external display accelerated, you have to connect that to the Puck, not the MBP.
3. You should use HDMI. In my setup, on DisplayPort I had blackouts, meaning the monitor going black, for about two seconds, reaching from once every couple minutes to once every ten seconds. Very annoying in a fight where you need to react fast.
4. If you just use the external screen, the screen will only switch on when the graphical interface starts. It will not show the Apple logo during boot, for example.
5. The integrated fan is audible, but a lot less so than my MBP freaking out temperature-wise and trying to keep a cool head.
The all important performance question:
In my setup (and please keep in mind that I am running a pretty big resolution) I see frame rates of 40-60fps in a High setting. Which for me is a huge improvement and makes the game really playable. Apart from that, I did not notice any adverse effects.
So, if any of you guys have questions, fire away. I will try to answer everything