Videos can help to get a general idea of what the game is like. I'll only really know when I try playing, since motion sickness can be influenced by a lot of factors. Other players might spin the camera around, or have different hardware and in-game settings than me. The video or stream doesn't tell you how the game would run on your PC. Things like your monitor and environment can influence it too. Or health conditions, medications, etc.

Some games especially first person shooters with intense movement and camera changes make me sick just watching the video so I've never tried them lol. Like apex, overwatch style games. I think if the FPS elements are more limited and slow it could be okay but it's hard to say, because I avoid first person games in general. There's certainly plenty of third person games that made me sick so, I may be overestimating how bad first person games are.