I have an RX Vega 56 Strix OC edition and it used to idle at around 30w. Now it idles at around 5W and it crashes in alll games. It isn't thermals cause it stays really cool.
I have dual monitors. I run a r5 2600x with 16gb of corsair vengeance rgb pro mem @3200mhz. I have a 1tb samsung ssd and a 1tb seagate hdd. The PSU is a Corsair RM750x. Also I don't really remember the actual idle wattage but im sure it was over 23W at least cause most of the time i'd be wacthing stuff on the internet and that's when i'd check the wattage with the AMD overlay.