Useful page of tips ~

Slightly older tip since the latest patch but turning the (flickering) shadows off and reducing the landscape detail helped to really smooth things further.

Switch landscape shadows to low or off. It helps a lot both with fps and stutters. Switch off clouds completely in difficulty(!) settings. Put buildings to very low.
Reduce texture quality from "original" to "quality" - important to avoid stutters.

Game settings to reduce/turn off for highest performance gain: SSAO, shadows, landscape shading, texture quality, landscape details.