1. I do think that it can work with an IW in front of an IWB.
2. I do not think it can work with an IF in front of an IWB.
The reason behind my thinking is that, in my mind, the IF comes inside even without the ball to occupy the half space. The IW will hold the width a tad better, coming inside with the ball.
I would imagine it works the best with a W, though, and that is also what I've been using in my current 4-3-3.