THE Nimzo Larsen begins 1.Nf3 followed by 2.b3. 1.b3 is LArsens penning and very unsound.
Since I answer 1.Nf3 with 1...Nc6, I am very happy if White insists on playing 2 b3 there.
2. d4 and it's a Queen pawn opening with your black knight blocking your c-pawn which sometimes is not a good thing.
Correct. Here's a game from a rated match:
THE Nimzo Larsen begins 1.Nf3 followed by 2.b3. 1.b3 is LArsens penning and very unsound.
Says who?
And at what level is it "unsound"?