Being a fan of both flight and racing sim I used to run a three monitor setup, however, a few months back I switched over to 4k in combination with track ir.
While the increased resolution is amazing, I do still miss my three monitor setup in some instances. With the three monitor setup you tend to rely more on peripheral vision than you realise at the time, it is only when that is removed, that you note its absence. It is especially obvious in racing sims where I no longer see cars drawing level out of the "corner of my eye", and I now have to rely on turning my head to shift the pov in game