The new AGESA version introduces support for S0i3, an active idle power state for Windows 10. S0i3 promises the low power consumption of S3 sleep coupled with quicker wake-up times. It's something Intel has been supporting for many years.
Additionally, the update promises better memory overclocking stability in the 1800-2000MHz FCLK range, as well as general, undefined stability improvements. There's also a vague reference to support for passive X570 motherboards, which may imply tweaks to power profiles for fanless X570 motherboards.
New AGESA 126.96.36.199 BIOSes are coming in January and February for @AMD Ryzen 5000 Series processors.— AMD Ryzen (@AMDRyzen) January 5, 2021
? Win10 s0i3 support
? Stability tuning for 1800-2000MHz FCLK (OC)
? Support for passive X570 motherboards
? General stability improvements pic.twitter.com/7wNyZk028H