Update:
I have accidentally found out that the Win 10 Game Mode is using CPU core affinity to optimize games (it looks for the fastest CPU cores while the game is running then will assign as many of the game's threads to them as it can).
I found this out by intentionally going into TM & manually setting CPU affinity to CPU cores 4,5,6,7 then after running the game I exited the game completely, opened another app then shut it down then went back into AHIII then opened TM to check CPU core affinity assignment to the AHIII running process (thinking that this should've reset itself back to all CPU cores...)....I found that the CPU core affinity was still assigned as I had assigned it prior..................
Hhhmmm..............I thought..........
So I devised a major test to see if Win 10 Game Mode was really remembering the CPU core affinity settings for AHIII & being saved to disk for reapplication as follows:
I went back into TM w\ AHIII running at initial screen & manually set the CPU core affinity for AHIII to CPU cores 2,3,6,7 (to split them across the 2 CCX units) then played the game to run in this config for Game Mode to see this then shut down the game then shut off my computer for 2 mins to allow all to completely power down & mem to drain completely so all will be reloaded from the SSD.
Then I restarted my box & when it got back to the desktop I started the game to the initial screen then opened TM to check the CPU core affinity settings for AHIII.....lo & behold they were showing to STILL be set as I had set them before I shut my box down (CPU cores 2,3,6,7).
This did not happen prior to me setting up AHIII to run w\ Win 10's Game Mode thru the Win 10 Game Bar so this has to be Win 10's Game Mode doing this. It was consistently splitting the game threads across the 2 CCX units w\o me doing anything but I now know that it will remember a manual CPU core affinity setting as well............
So it shows that Win 10 Game Mode is setting CPU core affinity to optimize a game's thread execution on a CPU either by picking the fastest CPU cores it sees on it's own to assign the game's threads to for optimization OR by remembering a manual CPU core affinity setting made for the game it is set up to optimize & assign the game threads to them as set.
As far as Game Mode doing other things to optimize a game I don't know at this time....but I DO know that Game Mode is using CPU core affinity to optimize game execution on Win 10 if it is enabled & set up for a game.
FYI........