I had a similar situation with two identical monitors except for some reason one of them was a slightly newer revision (same model!) and had an EDID that made i

I had a similar situation with two identical monitors except for some reason one of them was a slightly newer revision (same model!) and had an EDID that made it look as an 10bpc panel instead of 8bpc like the older revision. Setting both to 8bpc reduced the idle power consumption by 4x. If you are on windows, you may need some additional tool to be able to change the bpc (the AMD control panel applet works too).