I can’t say. I remember having good luck with the “Magewell USB Capture HDMI Plus”, but that is HDMI only. When I tested the 4K version, it was awful, but maybe not for this. “Magewell USB Capture HDMI 4K Plus Device.” How does CamTwist handle the live input?
It sounds dumb, but maybe there’s another way to get your feed into syphon and then share it with VDMX. (I’m also on a 2015 MBP w/ OSX 10.12 16GB).
Mokose makes an SDI HDMI UVC device that might be worth a try. mokose sdi/hdmi Mokose had the lowest latency in OBS for any of the other UVC capture devices: https://obsproject.com/forum/resources/capture-card-documentation-latency-decode-modes-formats-more.777/
Magewell didn’t score the best on that list ^ this is the specific mokose tested in that list.
lmk if any of this helps. thx