I have found something about the Link-Power-Management here in this (german) magazine: c't 6/2025 heise magazine
At page 92 is a test from Asus Prime B860M-A WIFI. They activated the C-States from the CPU and the Link-Power-Management from SATA and PCI Epress in Bios. Additionally you must modify the SATA Link Power Management in the Windows registry, you find the registry file here: ct.de/yrg9
After this modification the idle power drops down from 22W to 13W. I know you have the Z890M but I hope this registry mod will work on both chipsets.