Prop artifacts are definitely fps related on my system, but it's all over the place. The first time I tested it out I was getting intermittent white flickering blades (which I assume isn't a deliberate effect) only when my fps went up as
high as they could go, as can be seen in this video at 2:20 -
Then the next time I played the game the props had a different, larger, darker, constant kind of rotating flickering at all fps. Hopefully if they fix the blades disappearing altogether behind some types of cloud they'll also address some of these other inconsistencies at the same time.