You have the Optane module installed in the M.2 slot and your SSD in the 2.5" bay correct?
The Optane software will change the settings for you when you enable it. Leave your system set for AHCI, boot into Windows and install the Optane software. When you run the software and select Enable, the system will work for a moment and then ask to restart. When you do this it should boot into Windows using "RST with Optane" mode and you should be good to go. Wait a few minutes for the system to settle down and then reboot and you should notice it is much faster. You may not see as much of a speed increase since you are using an SSD already. Works best if you have a spinning HDD.