Unlike Null, Folded Man has been a frequent adversary for The Flash (and other DC heroes) in the comics.
The Flash appears to be making their Folded Man more of a metahuman than a genius with a supersuit, but he still seems like a perfect antagonist for new hero The Elongated Man to face in season 4.
The Flash TV show has released casting breakdowns for three new metahuman characters: Null, Crucifer and the Folded Man.
In the comics, Null, not to be confused with the relatively new villain The Null, is a very minor character.