BIOS, hmm I'm on 2202 and audio works fine for me, but I am also using Win7.
Maybe there's a Win10 issue here too, something to keep in the back of your mind.
The only time I ever had audio sync issues was when something else was running in the background pulling the system down.
Check to see how many services and things you have running in the background, also try disabling your antivirus when you play audio and see what happens.
Since you've been going at it already, I would start with the approach that you have to much bloat going on with system resources, and background services pulling at the system, and make sure everything is running nice and light.
NOW here's a complelty different approach here, BUT do you have a spare hard drive laying around?
Get another hard drive, unless you know how to mess with resizing partitions, being a geek and moving over some space and dual booting with Linux.
I would get Windows out of the picture for now, and install Linux and see how sound works in Linux, and if it works, then you'll know it's not a bad motherboard, it's just the software, and the system, something out of wack...
LEARN Clonezilla;
http://clonezilla.org/The reason I say Clonezilla, you install Windows, only the system, not any drivers, then make a backup.
Then you install only the drivers, make another backup.
Then start installing a few apps, make another backup.
Now if something breaks, you have a clean install to go back to and start over to work out problems from, it makes for an easier way to troubleshoot..