If you play on a crappy computer, here's something you NEED to know.
I have a 400$ 4 year old laptop. I usually get around 25 fps on medium settings. Today, I was playing around with the settings and realized if I took enviro to highest, and shadows to low, it would take my fps to 50-60. It may not look as good as my friends 1k desktop, but it runs as smooth.
TLDR: Shadows from medium to low is the biggest improvement in all the settings. IDK why, but do it.