J'ai vu ça sur reddit et ça parait fonctionner, je n'ai pas encore testé.
Here a 100% effective fix who include window mode borderless, but window mode alone is not enough. Follow those steps :
The CON of the fix is : no more online game. But if you don't care about that like me, this will make you happy.
I am currently running the game on a RTX 2070, at 60/65 outdoor and at a 80 fps indoor with no more stuttering or laging the last 2 hours of testing. On a personel graph setting between High/max.
1/ Get rid of Anti cheat. To do that : go to steamfolder\steamapps\common\ELDEN RING\Game, backup & rename the start_protected_game.exe . Take the eldenring.exe, make a copy, and rename the copy to start_protected_game.exe . (it is like havind 2 elder ring lauch exe but one is renamed dstart_protected_game.exe)
2/ download and install this : https://www.flawlesswidescreen.org/
3/ execute the elder ring plugin. Set "Framerate adjustement" to what your screen can handle. Then check "fix enabled", and "Aspect fix" and "Resolution fix" and "frame rate adjustement"
4/ execute elderring.exe. In game setting choose "Borderless window screen"
5/ Adjust your ingame graph setting according to your spec
6/ Start and enjoy this awesome game