I'm on a late 2019 MacBook Pro with an external monitor that has:

        B326HK:
          Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)
          UI Looks like: 1920 x 1080 @ 30.00Hz

In iStats, Radeon High Side shows 5.6-6W of power usage. But still, my CPU cannot sustain CPU frequency above 2Ghz for more than 5 minutes due to thermal throttling.