Configuration: I have a MacBook Pro 2017 with Touch Bar connected to a 27" external display and a very fast external HD connected via Thunderbolt-3.
Problem: I am unable to drive 4K or HD video in this configuration without constantly dropping frames (in Davinci Resolve.) When I disconnect the external display and use only my laptop's display, the video plays significantly better -- almost perfect.
Hypothesis: I suspect the original configuration is a heavy lift for my laptop's graphics chip. And the video may play fine if it is driving only one monitor instead of two.
Goal: I want to use my external display and not my laptop's internal display -- all the while keeping my keyboard and mouse functional. (No, I do not want to turn the brightness down to 0 nor do I want to do mirroring.)
How do I do this?
Thanks in advance.