Makes my 2018 "Pro" machine feel like an 8 year old device struggling to keep up with very basic tasks because of thermal throttling (and this is even after getting the fans cleaned by Apple recently)
Mine is 3840x1600 (38") and MBP 15.4 (with discrete AMD graphics) and fans never spin up just because it is hooked on external screen.
If you haven’t already, try plugging the power in on the right side, and the display/any other peripherals on the left. It sounds crazy, but this has been the solution for tons of people. Apparently the heat generated by power input (even at a steady full charge) is enough to spike the sensors near the components on the left side.
I haven’t experienced any downsides to this change other than having to spend a few minutes rearranging stuff on my desk.
1. Plug it all in right side and see how it goes. The important part is that power needs to be on the right, the point of plugging other stuff on the left is just to distribute heat/load.
2. If that doesn’t help/causes other issues, are you willing to separate power delivery and plug in two cables? I know it’s annoying when the spec supports single-cable everything, but in the scheme of things it’s not a terrible trade off to have a more usable machine.