Macbook Pro 16" laptops with the 5300M and 5500M dedicated GPUs run with Radeon High Side at 20W when connected to an external monitor. This causes the machine to run VERY hot and the fans to spin to over 5000rpm.
The EXACT SAME LAPTOP running the Windows drivers through Apple bootcamp do not have this issue.
The MacOS drivers for the Radeon 5300M and 5500M need to be updated to fix this!
Here is a thread with over 2300 replies about this WIDESPREAD problem: