Yes, this!
My GTX 970 could do this, you could add and remove monitors from the Nvidia surround setup and have 3 monitors grouped for widescreen gaming and a 4th for email/browsing/mp3 etc.
I can't see how to do this in the cluttered Radeon setup, which has exactly zero options for eyefinity and doesn't let you pick which monitors you want grouped!
I'm sure it used to some years ago?
I'm using 3 x 22" monitors and 1 x 42", I obviously do NOT want the 42" grouped in an Eyefinity group!