If you put your computer to sleep in one of these modes and find it immediately wakes back up again, fans whirring, login-screen ablazing, open a Command Prompt as Administrator (right click on the Command Prompt icon in the Start Menu>Accessories and select “Run as Administrator”). Then type:

powercfg -lastwake

You’ll likely see something like I did, and see a USB Root Hub caused the start.

type

powercfg -devicequery wake_armed

and it’ll give you the names of the devices that actually caused the wake-up signal to fire. For whatever reason, my Keyboard and Mouse both seemed to be culprits so I disabled them both by typing:
powercfg -devicedisablewake “HID-compliant Mouse”
powercfg -devicedisablewake “HID-Compliant Keyboard”

case was sensitive for those names and they matched the output from the “wake_armed” device query above. That did it, allowing my machine to sleep properly. Waking up now has to be done from the power button on the front of the case.

There are some additional tips in this post on vistax64.com which I may experiment with if I get the time, but the current setup is good for now.