Soldato
Yes, you are correct, the Oculus demo scenes and Superhot are fine. But Alien Isolation and Half Life Alyx which I have only played for about 10 minutes each so far are making me feel quite nauseating. Probably because of both the decoupling and yes I have set the turning to smooth and not snapping as that is ultimately how you want to experience it, although like you say it might be beneficial to start with the Snap.
Try Alyx with teleporting it will alleviate the motion sickness. Then once you have used teleporting in VR try actual motion. Even now I still cant stomach some games unless I use teleporting.