I think that's pretty much it. If game run not in fullscreen - it's run well, otherwise it's stuttering. That problem reveals himself from time to time.
Changing vsync setting doesn't help, only help is to change full screen mode to window mode.
GPU drivers 20.9.1 that's not the last version but game was fine with it all the way before.
It is not impossible that one of the latest game updates works better with a gpu update. But in any way: if nothing helps I would recommend reaching out to CDPR support: https://support.cdprojektred.com/en/gwent/pc/gwent-technical/issue/61/my-game-crashes (please click on "CONTACT US" to send a ticket - and yes, this article is not about the exact same topic but since there is no support article that fits your problem, this is the closest one).