yep… I had it On… and Off… Zero diff noticed… I guess it is in meanwhile only that you not get any “important” windows messages while in-game 
For some users the HAGS (GPU) will bring bit more fps ( dont’ expect magic ) . For other users it has the opposite effect. I have trouble with this in generally, because depend on windows update it let reboot my PC randomly and so I not use it. And as it worked a while without issues, I also noticed no higher fps ( +/-5 is out of my attention ).
PS.: I also not realy use the dev-mode… I let e.g. afterburner run