I recently started this game, and my first impression using multi-monitor resolution of 4360x1440 with FoV = 120 was okay. Borderless window mode seems to work pretty well.
But later on, I noticed some problems:
a planet changing color when in peripheral vision;
weapons and hands look bulky;
some menus (crafting, IIRC) having some content duplicated or too far on the sides.
So I decided to postpone this game and hope for better ultrawide / multi-monitor support.
@Shyla - is your current work targetting 21:9 / 24:10 specifically, or can I hope to get better non-standard wider aspect ratio support, too?