Not sure if there's a difference between No DQ and No Holds Barred....only difference I can think of is No DQ allows weapons, illegal holds and outside interference, while No Hold Barred only allows weapons and illegal holds (I could be wrong)
But I'm sure in a No DQ/No Holds Barred match, you have to pin/make your opponent submit in the ring, whereas in a Street Fight you can finish (or even start) the match anywhere in the arena, e.g. the Parking Lot Brawl between Cena and Eddie Guerrero