@deus_rsf i agree, don’t use the ultra, even when everybody says that GPU like RX 570 and 580 are supposed to have 60fps at 1080p in every game, because this isn’t like every game, both in good and in bad. In this game, you have to make compromises, and it won’t destroy your gaming experience, unless you are just after the graphical eye candy. This game is close to a historical masterpiece in many ways, and if you can get your mind in this game, you can enjoy the game even with medium settings.
To get best experience, try different graphics settings and see your self. Its pretty fast to adjust couple settings at time (not from worst to best but like 1-2 levels at time), so its pretty easy to test, and even change your settings when you come to cities / villages, or if you go out to forest for a while. Villages and castles are very texture hungry, and that will put many GPU’s under massive stress, in both GPU clock and memory.