Unless you disable VSync, which is not easy to do on a Mac, your refresh rate is going to be capped at 60.on the GFX graphs 60 is the high value, and droping is going down on GPU.
what's your external display (resolution and refresh rate)?so problem cause only when external display is connected by hdmi....
hello format my macbook pro 2017 ..
[2.9 ghz core i7
16gb ram
Amd radeon pro 560 4gb vram]
What kind of cable/adapter are you using to connect to your external display/projector?About external displays i tested it with normal monitor, full hd, and with projector, its not depend what is connected but i think by what, and then its causing problem, because when i use ndi both cpu and gpu work without dropping frames, its show after sending phusical output.