No worries, every help is much apprecciated!

Sadly I have tried those solutions but with no luck, my Game Mode in W10 is disabled already and my GPU card isn't OC'ed (neither by me or factory), about overlay I got none, I stayed away from Steam client exactly because of that, and I have disabled my Nvidia GeForce Experience Overlay, nothing works...
I don't really understand what troubles FFXIV client, I could play just fine before the W10 update and now, boom, no DX11 for me, while every other games run just fine... I wish I could check some Crash Log atleast but I didn't find any in FFXIV client files, and the Launcher Crash isn't reported in W10 Events Log either... I don't know what to do.