I don't know. I almost always read the plot of the movie before I watch it, and I still enjoy it. I also watched at least 4 playthroughs of the first Silent Hill before I played it myself, and I still really enjoyed it.
Same. I've never had a game/movie/book ruiend for me for knowing some, if not all of the plot beforehand. Hell Sometimes I ask a few of my friends what the plot is all about, rather than constantly diving into everything and not knowing if it will be garbage or not, I'd rather know how good the plot is going to be in order to gain interest.
I watched Jacksepticeye playing Night in the Woods from start to finish and watching him was what got me interested in buying and playing the game.