This appears to be a software bug in macOS or AMD's drivers. Plugging in an external monitor at certain resolutions (1440p@60Hz in my case) will cause the AMD GPU to draw 18-20W constantly, no matter what it's doing. This causes the total system draw to increase from ~10W to ~30W. All that heat has to go somewhere. If I change the resolution of my external monitor to 1080p the AMD GPU drops to ~4W and the fans are qu…
This is a bug on Macbooks in general, as I understand it. I have a 2019 MBP with a 4k monitor, and if I change the resolution to anything except the default, there is massive system-wide lag. God forbid I use PyCharm on 4k scaled resolution – a full second between typing and seeing the text.
This seems to be excessive GPU use when simply connecting an external monitor at its native res.